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Agricultural  Experiment  Station, 


BULLETIN    NO.    98. 


THE  CURCULIO  AND  THE  APPLE. 


BY  CHARLES  S.  CRANDALL. 


URBANA,  FEBRUARY,  1905. 


SUMMARY  OF  BULLETIN  No.  98. 

1.  The  investigations  reported  in  this  bulletin  were  undertaken  because  of 
serious  and  widespread  injury  to  the  apple  crop  by  curculios.  Page  468 

2.  The  larvae  of  the  plum  curculio  develop  in  very  small  apples,  and  the  fall 
of  the  fruit  is  necessary  to  their  development.     The  time  from  oviposition  to  the 
emergence  of  the  larvse  from  the  fruit  varies  from  sixteen  to  thirty-nine  days,  the 
average  in  1903  being  twenty-six  days,  and  in  1904  twenty  days.  Page  475 

3.  The  mortality  of  plum  curculio  larvse  in  the  fruit  is  due  to  crushing  by 
growth  of  the  fruit  tissue,  and  to  the  action  of  the  sun.  Page  479 

4.  The  depth  of  pupation  of  the  plum  curculio  varies  from  one-fourth  inch 
to  three  and  one-half  inches;  93.69  percent  of  the  824  pupse  recorded  were  at  depths 
of  two  inches  or  less.  Page  480 

5.  The  time  the  plum  curculio  spends  in  the  ground  ranges  from  nineteen  to 
forty-eight  days,  the  average  being  twenty-eight  days.     In  1904,  87  percent  were 
in  the  ground  between  July  10th  and  August  8th,  and  97  percent  between  July  10th 
and  September  1st.  Page  487 

6.  The  first  plum  curculio  beetle  emerged  from  the  ground  July  17th,  and  the 
last  on  November  7th,  a  period  of  one  hundred  and  fourteen  days.     The  newly 
emerged  beetles  feed  freely  upon  the  fruit  and  do  great  damage.  Page  490 

7.  The  beetles  of  the  plum  curculio  hibernate,  and  appear  the  next  spring 
early  in  May.     No  evidence  was  found  of  their  feeding  upon  leaves  or  buds  in  the 
orchard.  Page  495 

8.  Oviposition  of  the  plum  curculio  begins  while  the  apples  are  very  small, 
and  may  continue  until  September.     The  largest  number  of  eggs  laid  by  one  indi- 
vidual was  263,  and  the  longest  period  during  which  one  individual  laid  eggs  was 
one  hundred  and  five  days.  Page  498 

9.  The  habits  and  life  history  of  the  apple  curculio  differ  from  those  of  the 
plum  curculio.  Page    515 

10.  The  period  of  oviposition  of  the  apple  curculio  is  about  sixty  days.     The 
number  of  eggs  laid  by  twenty  females  varied  from  four  to  one  hundred  and  twenty- 
two  for  each  individual.  Page  521 

11.  The  larva?  of  the  apple  curculio  change  to  pupa;  within  the  fruit,  and  the 
adult  beetles  emerge  directly  therefrom.  Page  515 

12.  The  plum  curculio  and  apple  curculio  each  have  certain  characteristics 
whereby  they  can  be  readily  distinguished.  Page  528 

13.  Various  means  of  controlling  curculios  have  been  tried.  Page  530 

14.  Experiments  at  Barry  in  1903  showed  practically  no  gain  from  spraying. 
The  results  were  affected  by  weather,  location,  and  abundance  of  insects.     Page  533 

15.  Spraying  experiments  in  1904  resulted  in  a  range  of  benefit  from  14.14 
percent  to  60.96  percent.     Four  or  five  applications  will  probably  control  from 
twenty  to  forty  percent  of  the  possible  injury.  Page  541 

16.  Cultivation  of  the1  ground  aids  greatly  in  the  repression  of  curculios. 

Page  553 

17.  Conclusions.  Page  556 


THE  CURCULIO   AND  THE  APPLE. 

BY  CHARLES  S.  CRANDALL,  ASSISTANT  CHIEF  IN  POMOLOGY. 

INTRODUCTION. 

In  all  sections  of  the  State  of  Illinois  where  orchard  fruits  are  grown 
may  be  found  fruits  that  are  more  or  less  defaced  by  deformities,  by  curi- 
ously made  surface  cuts,  and  by  small  cylindrical  excavations.  These 
marks  are  found  upon  plums,  peaches,  apples,  and  less  commonly  upon 
pears  and  quinces.  The  same  marks  are  common  on  fruits  of  the  wild 
plum,  wild  crabapple,  and  of  the  red-fruited  hawthorn  so  common  in 
native  woodland.  The  marks  referred  to  are  made  by  two  species  of 
curculio,  and  from  reports  received  by  the  Horticultural  Department  of 
the  Experiment  Station,  and  also  from  observations  made  by  representa- 
tives of  the  Station,  it  appears  that  during  the  last  two  or  three  years 
there  has  been  a  decided  increase  in  the  amount  of  injury  resulting  from 
the  attacks  of  these  insects. 

The  amount  of  injury  done  to  the  apple  crop  is  not  the  same  every 
year,  nor  is  the  damage  equally  distributed  over  the  state.  In  some 
counties  the  fruit  is  comparatively  free  from  injury,  while  in  others  the 
damage  practically  amounts  to  the  loss  of  the  whole  crop. 

From  personal  inspection  of  orchards,  it  appears  that  no  section  is 
entirely  free  from  attack,  but  there  are  certain  factors  of  location  and 
of  orchard  treatment  that  in  great  measure  account  for  differences  in  the 
amount  of  injury  inflicted  in  different  sections.  Orchards  in  close  prox- 
imity to  bodies  of  timber  suffer  more  than  do  those  remote  from  wooded 
parts,  and  orchards  where  clean  cultivation  is  practiced  are  remarkably 
free  from  injury  when  compared  with  orchards  in  which  grass  and  weeds 
grow  undisturbed. 

The  injuries  to  apples  which  are  to  be  considered  in  this  bulletin  are 
not  new.  The  same  trouble  has  been  complained  of  for  many  years;  but 
there  have  been  periods  when,  from  natural  causes,  the  work  of  the  in- 
sects has  been  minimized,  and  now  that  this  period  of  comparative  im- 
munity has  been  followed  by  an  ascending  movement  towards  maximum 
injury,  the  difficulty  is  brought  to  the  notice  of  many  fruit-growers  for  the 
first  time,  and  to  them  it  is  new  and  strange.  As  far  back- as  1860,  serious 
injury  to  plums  and  peaches  was  reported  from  southern  counties,  and  in 
1867  and  1868  not  only  the  plums,  peaches,  and  apples  of  the  southern 
counties,  but  the  apples  of  northern  counties,  were  seriously  injured. 

467 


468  BULLETIN    No.  98.  \Februury. 

The  insects  reponsible  for  the  injuries  above  referred  to  are: 
The  Plum  Curculio — ConotracJiclus  m/////>//or,  Herbst. 
The  Apple  Curculio — Anthonomus  quadrigibbus,  Say. 

There  is  a  third  species — the  Plum  Gouger,  Anthonomus  prunicida — 
which,  though  in  the  main  confining  its  work  to  the  plum,  has  been  re- 
ported as  attacking  the  apple;  but,  as  in  our  work  with  the  apple  in  the 
past  two  seasons  not  a  single  specimen  of  the  gouger  was  found,  nothing 
further  need  be  said  of  this  species. 

The  two  species  of  curculio  to  be  considered  differ  in  appearance,  in 
habits,  and  in  development,  and  there  is  a  corresponding  difference  in  the 
character  of  the  injury  they  inflict.  Both  are  natives  that  have  lived  on 
and  bred  in  native  food  plants  for  unknown  generations.  The  apple  cur- 
culio once  lived  exclusively  upon  fruits  of  the  wild  cra-bapple  and  the 
hawthorn.  With  the  introduction  of  cultivated  fruits  of  congeneric 
species,  it  took  kindly  to  them,  and  is  now  as  much  at  home  on  our  best 
orchard  apples  as  on  the  less  inviting  wild  crab.  The  plum  curculio, 
supposed  to  have  been  originally  confined  to  the  native  wild  plums  as 
food  plants,  has  evidently  developed  new  tastes,  for  it  feeds  on  and  breeds 
in  both  wild  crab  and  hawthorn  as  well  as  in  wild  plum. 

Among  cultivated  fruits,  while  it  is  generally  understood  that  the 
plum  curculio  belongs  to  and  prefers  the  plum,  it  has  a  well-developed 
taste  for  peaches  and  cherries,  seems  perfectly  satisfied  with  the  apple, 
and  will  under  necessity  accept  pears  and  quinces. 

Our  present  consideration  of  the  insects  relates  to  the  apple  only. 
Both  species  feed  upon  and  breed  in  it,  and  they  both  do  it  injury.  In 
general,  it  is  the  plum  curculio  that  does  the  greater  amount  of  damage , 
but  from  some  of  the  southern  counties  it  is  reported  that  the  apple  cur- 
culio is  the  more  destructive  of  the  two. 

WHY  AN   INVESTIGATION  OF  CURCULIO   WAS 
UNDERTAKEN. 

.  In  October,  1902,  Messrs.  Albert  Blair  and  John  R.  Williams,  pro- 
prietors of  extensive  orchards  near  Barry,  in  Pike  County,  appealed  to 
the  Station  authorities  for  assistance  in  determining  the  cause  of,  and  in 
finding  a  remedy  for,  very  destructive  work  done  in  their  orchards. 
Their  crop  in  1902  was  practically  ruined,  and  previous  crops  had  been 
in  some  degrees  injured.  Reports  of  similar  injuries  were  received  also 
from  other  fruit-growers  of  the  same  section.  Specimens  of  injured 
apples  were  shown  which  fully  supported  the  reports  of  injury  done. 
The  gentlemen  mentioned  represented  over  two  hundred  and  sixty  acres 
of  orchard,  nearly  half  in  full  bearing,  the  rest  approaching  bearing  age. 
The  trouble  was  not  confined  to  a  few  orchards,  but  was  general  through- 
out the  county.  The  apple  industry  of  Pike  County  is  a  large  one;  or- 


1905. 1  THE   CURCULIO    AND  THE  APPLE.  469 

c hards  of  commercial  size  are  numerous,  and  the  aggregate  acreage  is 
extensive.  The  losses  sustained,  while  not  equal  in  all  orchards,  were 
everywhere  serious,  and  would  together  represent  a  large  sum. 

These  facts  together  with  the  reported  losses  from  the  same  cause 
from  other  and  widely  separated  counties  served  to  show  that  the  problem 
was  of  importance  to  the  whole  state;  therefore  it  was  a  problem  falling 
legitimately  within  the  province  of  the  Experiment  Station. 

After  full  discussion  with  the  Director  of  the  Station  and  the  Depart- 
ment of  Entomology  it  was  decided  that  the  Department  of  Horticulture 
should  undertake  an  investigation  of  the  difficulty. 

It  was  perfectly  plain  from  inspection  of  injured  apples  that  the  de- 
structive work  was  done  by  curculios,  but  there  was  then  some  doubt  as 
to  whether  one  or  more  species  was  responsible,  and,  if  more  than  one, 
which  did  the  greater  damage.  A  preliminary  examination  of  the 
orchards  was  made  in  November,  1902,  at  which  time  specimens  of  both 
plum  curculio  and  apple  curculio  were  found  in  hibernating  quarters. 
The  investigation  was  commenced  in  April,  1903,  carried  through  the 
season,  and  continued  through  the  season  of  1904,  along  two  principal 
lines.  First— Spraying  with  arsenical  poisons.  Second — Inquiry  into 
the  life  histories  and  habits  of  the  two  insects  with  a  view  to  the  pos- 
sible discovery  of  vulnerable  points  which  might  suggest  new  lines  of 
attack. 

Because  of  the  differences  between  the  two  species  already  alluded 
to,  it  will  be  necessary,  or  at  least  advisable,  to  consider  them  separately, 
and  precedence  must  be  accorded  the  plum  curculio,  not  only  because  it 
is  best  known  and  has  been  longest  known,  but  because  it  is  usually  the 
more  destructive  to  apples.  Both  insects  are  to  be  considered  in  their 
relations  to  the  apple  only. 


THE  PLUM  CURCULIO. 
HISTORICAL. 

The  plum  curculio  was  first  discovered,  named,  and  given  systematic 
position  by  Herbst  in  1797,  but  the  insect  was  known  as  injurious  to 
plums  and  cherries  long  before  this.  The  first  published  account  of  the 
habits  of  the  insect  appeared  in  the  "Domestic  Encyclopaedia"  published 
at  Philadelphia  in  1803,  and  was  written  by  Dr.  James  Tilton  of  Wilming- 
ton, Delaware.*  This  article,  in  an  enumeration  of  the  fruits  attacked, 
includes  not  only  the  stone  fruits,  but  the  apple,  pear,  and  quince  as  well. 
It  appears  from  this  that  the  habit  of  attacking  the  apple  is  an  old  one 
and  not  a  development  of  recent  years  as  some  have  suggested. 

*Harris.      Insects  Injurious  to  Vegetation.      Page  76. 


470  BULLETIN    No.  98.  [February, 

Through  the  early  years  of  the  nineteenth  century  agricultural  jour- 
nals made  numerous  references  to  the  injuries  done  by  the  curculio  and 
to  the  success  or  failure  of  the  remedies  tried.  About  1830,  a  lady  in. 
New  Jersey  started  a  movement  to  raise  $2,000  by  subscription  to  be 
offered  as  a  premium  for  the  discovery  of  an  effective  means  of  destroying 
the  curculio.  A  committee  of  the  Massachusetts  Horticultural  Society 
appointed  to  consider  the  proposition  recommended  that  $200  be  appro- 
priated for  the  purpose  by  the  society  and  that  subscriptions  should  be 
opened  to  add  to  the  amount.  It  is  not  known  that  any  person  ever 
claimed  this  premium.*  March  5,  1842,  the  Massachusetts  Horticultural 
Society  voted  to  offer  a  premium  of  $100  for  a  successful  method  of  des- 


/T 
PLATE  1.     THE  PLUM  CURCULIO,  ENLARGED. 

troying  the  insect,  and  an  equal  amount  was  added  to  this  sum  by  sub- 
scription, f 

It  appears  that,  although  there  were  several  applicants,  this  premium 
was  never  paid,  for  the  reason  that  no  method  presented  was  thought 
sufficiently  successful.  The  paper  most  highly  commended  was  one 
by  Dr.  Joel  Burnett,  giving  something  of  the  habits  and  life  history  of 
the  curculio  and  recommending  the  now  well-known  jarring  process  as 
a  remedy.  This  paper  was  published  in  the  proceedings  of  the  society 
for  1843,  and  also  in  Hovey's  Magazine  for  the  same  year. 

Kenrick  (New  American  Orchardist,  2d  Ed.,  1835,  page  49),  refers 
to  the  plum  curculio  as  "the  most  destructive  of  all  enemies  to  fruit/' 
and  includes  the  apple  and  pear  in  the  list  of  fruits  attacked.  Of  the 
apricot,  nectarine,  and  plum  he  says:  "The  destruction  is  usually  almost 
total  in  those  parts  of  the  country  where  this  insect  abounds,"  but  the 
apple  "usually  survives,  although  disfigured  in  its  form  and  lessened  in 
its  size." 

*History  Massachusetts  Horticultural  Society.     Page  257. 
tHistory  Massachusetts  Horticultural  Society.     Page  256. 


1905.]  THE   OUKCULIO   AND  THE  APPLE.  471 

The  organization  of  horticultural  societies  and  the  establishment  of 
journals  devoted  especially  to  horticultural  questions  kept  pace  with 
advances  in  fruit  growing  and  afforded  means  of  recording  experiences 
and  discussing  theories  regarding  curculio.  These  sources  supply  many 
references  to  the  curculio,  and  when  collected  and  digested,  these  refer- 
ences exhibit  marked  uniformity  in  tone.  They  refer  mainly  to  losses 
sustained,  or  detail  the  failure  or  successful  application  of  some  remedy. 
Discussions  of  treatment  are  frequent  and  often  bring  out  statements  of 
results  directly  opposed  to  each  other,  although  based  upon  identical 
treatment.  Some  new  remedy  is  heralded  as  the  salvation  of  fruit- 
growers one  year  and  is  bitterly  condemned  the  next.  It  does  not 
appear  that  there  was  any  marked  advancement  towards  perfectly  suc- 
cessful control.  In  some  sections,  plum  culture  was  abandoned  and, 
in  general,  fruit  men  were  not  encouraged  to  plant  on  a  commercial 
scale. 

Most  of  the  early  testimony  concerning  the  insect  has  reference  to 
the  plum  only,  or  to  the  stone  fruits.  Few  make  serious  complaint 
of  injury  to  the  apple,  but  enough  to  show  that  the  curculio  did  work  on 
the  apple,  though  usually  not  causing  such  serious  loss  as  to  discourage 
growers. 

The  natural  food  plant  of  the  plum  curculio  is  indigenous  to  the 
timbered  porticos  of  Illinois,  and  we  may  fairly  assume  that  the  plum 
curculio  was  present  in  the  state  before  the  introduction  of  cultivated 
fruits.  The  insect  probably  attacked  stone  fruits  soon  after  their  culti- 
vation began,  but  no  date  can  be  assigned  for  the  first  depredations. 
The  earliest  reference  to  curculio  thus  far  found  is  by  John  A.  Kennicott, 
chairman  of  the  committee  for  Illinois,  who  reported  on  the  horticultural 
interests  of  this  state  to  the  "American  Pomological  Congress,"  assem- 
bled at  Syracuse,  New  York,  September  14,  1849.  Of  the  curculio  he 
says:  "The  plum  tree  succeeds  to  admiration  on  our  deep  prairie  soils 
and  'sets'  enormous  crops  of  fruit.  But,  alas,  the  curculio  makes  sad 
havoc,  and  often  leaves  us  scarce  a  single  unmarked  specimen.  Most 
of  our  best  soils  are  light  'sandy  loam'  and  this  is  the  proper  home  of  this 
'hump-backed  little  Turk/  where  he  winters  unharmed  and  breeds  and 
multiplies  to  an  extent  which  threatens  the  ultimate  abandonment  of 
this  and  other  beautiful  and  delicious  fruits  of  its  class,  unless  a  more 
practicable  remedy  than  any  now  attempted  should  be  discovered."* 

All  early  references  to  the  plum  curculio  convey  the  idea  that  it  is 
an  old  offender,  and  there  appears  to  be  no  doubt  that  from  the  beginning 
of  fruit  culture  in  the  state  the  curculio  regularly  preyed  upon  all  stone 
fruits  and  frequently  did  serious  injury  to  the  apple.  Mr.  D.  B.  Walsh, 
one  of  the  editors  of  the  American  Entomologist,  writes  in  that  journal 
for  1868  of  a  trip  around  the  state,  and  among  other  things  says:  "Noth- 

*Patent  Office  Report.     Agriculture,  1849.     Page  441. 


472  BULLETIN    No.  98.  {February. 

ing  in  the  course  of  this  Southern  tour  surprised  me  more  than  the  whole- 
sale manner  in  which  pip-fruit  in  the  South  is  punctured  and  ruined 
by  various  kinds  of  snout  beetles.  In  the  North  it  is  quite  unusual  to 
see  an  apple  bearing  the  well-known  crescent  cut  of  the  common  curculio, 
but  in  the  South  I  estimated  that,  upon  an  average,  every  apple  bore 
three  such  cuts.  When  I  got  to  Lacon,  which  lies  but  little  to  the  south 
of  Rock  Island,  the  comparative  immunity  of  the  apple  crop  from  this 
grievous  pest  became  apparent  at  once,  but  in  Madison  County,  in  Jersey 
County,  in  Macoupin  County,  in  Union  County,  in  Pulaski  County,  and 
in  Champaign  County,  the  apples  seemed  to  be  almost  universally  crum- 
pled and  gnarled  by  the  punctures  of  fruit  borers."* 

Mr.  Walsh  divides  the  injury  between  the  two  species  here  consid- 
ered, and  undoubtedly  his  list  of  counties  where  injury  was  apparent 
would  have  been  longer  had  he  visited  more  counties.  The  published 
proceedings  of  the  state  and  local  horticultural  societies  for  this  period 
and  for  a  few  succeeding  years  show  that  the  curculio  was  regarded  as  a 
serious  pest  by  all  fruit-growers. 

GEOGRAPHICAL  DISTRIBUTION. 

As  the  plum  curculio  is  native,  it  may  reasonably  be  supposed  that 
its  distribution  would  nearly  coincide  with  the  distribution  of  its  native 
food  plants.  The  original  and  natural  food  plant  of  the  plum  curculio 
is  the  wild  plum,  although  it  frequently  feeds  upon  and  oviposits  in»fruit 
of  the  wild  crab-apple  and  the  hawthorn.  The  distribution  of  the  insect 
is  nearly,  but  possibly  not  quite  so  extended  as  is  the  distribution 
of  the  wild  plum.  The  insect  is  known  from  Canada  to  the  Gulf  and 
from  the  Atlantic  west  to  the  one  hundredth  meridian,  and  possibly  in 
some  places  west  of  this  line.  It  had  not  appeared  in  Colorado  up  to 
the  spring  of  1902. f  It  has  not  reached  the  Pacific  coast  states,  and 
with  one  exception  has  not,  so  far  as  the  writer  has  been  able  to  ascer- 
tain, been  reported  west  of  the  Continental  Divide.  This  exception  is 
a  report  in  the  spring  of  1902  of  its  appearance  in  the  Bitter  Root  Valley 
in  Montana.! 

*American  Entomologist,  October,  1868,  page  36. 

tGillette.     Colorado  Station  Bulletin  71,  page  14.     April,  1902. 

JExperiment  Station  Record  13,  page  805. 


1905.]  THE   CURCULIO   AND  THE   APPLE.  473 

HABITS   AND   LIFE   HISTORY   OF   THE   PLUM 
CURCULIO. 

In  order  to  combat  intelligently  any  injurious  insect,  it  is  essential 
that  the  habits  and  characteristics  be  known.  Every  detail  of  the  full 
life  cycle,  from  deposition  of  the  egg  to  the  maturity  and  death  of  the 
perfect  insect,  must  be  inquired  into,  and  special  effort  given  to  the 
.correct  interpretation  of  the  observed  habits  of  those  insect  forms  or 
stages  directly  responsible  for  the  injury  done.  If  there  are  vulnerable 
points  in  the  economy  of  any  particular  insect,  study  of  habits  will 
reveal  them;  then,  knowing  the  weak  points,  mean  "can  be  devised  for 
attack. 

The  life  cycle  of  the  plum  curculio  is  as  follows:  At  about  the 
time  in  early  spring  when  vegetation  resumes  activity  and  buds 
begin  to.  push,  curculios,  which  have  hibernated  under  rubbish  on 
the  ground,  under  the  rough  bark  of  trees  and  in  other  secure  hiding- 
places,  emerge  from  concealment  and  seek  the  fruit  plants  upon  which 
they  feed  and  breed.  About  the  time  the  trees  bloom,  mating  begins  and 
as  soon  as  the  young  fruit  enlarges  the  deposition  of  eggs  begins.  Apples 
no  larger  than  small  peas  often  bear  from  one  to  three  of  the  character- 
istic crescent  marks  made  by  this  curculio.  The  deposition  of  eggs  goes 
on  most  rapidly  during  the  month  of  June,  but  continues  through  July 
and  August,  gradually  growing  less  and  less  as  the  beetles  die.  The 
majority  of  the  beetles  of  this  generation  do  not  live  beyond  the  month 
of  July,  but  a  few  may  survive  until  September,  or  in  rare  instances  until 
late  fall.  During  the  season  both  males  and  females  feed  upon  the  same 
fruits  in  which  eggs  are  deposited,  making  small,  usually  cylindrical, 
punctures.  The  eggs  hatch  in  from  four  to  six  days  and  the  young  larvae 
start  tortuous  burrows  through  the  fruit.  Development  of  the  larvae 
causes  the  fruit  to  fall  within  a  few  days.  In  about  twenty  days  the 
larvae  mature,  cease  feeding,  bore  out  of  the  fruit,  and  at  once  enter  the 
ground  where  they  complete  their  transformations  and  in  about  twenty- 
eight  days  emerge  as  perfect  beetles.  The  newly  emerged  beetles  usually 
remain  quiet  for  a  day  or  two,  allowing  the  body  wall,  beak,  and  jaws 
to  harden ;  then  they  fly  into  the  trees  and  begin  feeding  upon  the  fruit. 
Beetles  of  this  new  generation  do  not  (except  possibly  in  rare  cases)  pair 
and  no  eggs  are  laid  during  this  first  season.  The  fruit  is  freely  punctured 
for  feeding  purposes  and  the  amount  of  this  work  increases  as  the  season 
advances.  It  is  this  feeding  of  the  new  generation  that  causes  the  greatest 
injury  to  the  fruit  crop.  Feeding  continues  as  long  as  fruit  remains  upon 
the  trees.  Late  in  the  fall  the  beetles  leave  the  trees  and  hide  away  in 
secure  places  for  the  long  winter  period  of  hibernation.  Such  in  brief 
is  the  life  history  of  the  plum  curculio. 


474  BULLETIN    No.  98.  [February, 

STAGES   IN   THE   DEVELOPMENT  OF   THE   PLUM 
CURCULIO  CONSIDERED  IN  DETAIL. 

Having  stated  the  main  points  in  the  life  of  the  insect,  we  will  now 
take  up  the  various  stages  for  more  detailed  consideration,  embodying 
such  facts  as  have  been  gleaned  from  the  writings  of  others,  together  with 
our  observations  as  made  during  the  two  seasons  1903  and  1904. 

THE  EGG. 

The  egg  of  tha  plum  curculio  may  be  described  as  oblong-oval  in 
shape,  and  from  several  measurements  made,  is  found  to  vary  be- 
tween .025  inch  and  .04  inch  in  length  with  a  transverse  diameter  equal 
to  about  one-third  the  length.  When  fresh  laid  the  egg  is  shining  white, 
but  within  a  short  time  becomes  dingy  and  even  yellowish.  Sometimes 
the  egg  cavities  are  not  of  sufficient  depth  to  cover  the  egg  fully,  and  in 
such  cases  the  portion  exposed  to  light  and  air  assumes  a  dark  brown 
color  and  becomes  more  or  less  corrugated  from  loss  by  evaporation. 

Regarding  the  duration  of  the  egg  period,  writers  on  curculio,  so  far 
as  consulted,  give  only  general  .statements,  which  place  the  time  between 
four  and  seven  or  more  days.  June  13,  1904,  the  exact  time  of  ovi- 
position  was  recorded  in  six  cases,  and  subsequent  observations  were  made 
to  determine  the  exact  time  of  hatching.  Discarding  fractions  of  hours, 
it  was  found  that  one  egg  hatched  in  96  hours  or  four  days,  one  in  105 
hours  or  four  days  and  nine  hours,  and  four  in  108  hours  or  four  and  one- 
half  days.  This  was  in  the  laboratory  under  inside  conditions.  With- 
out doubt  temperature  and  other  weather  conditions  influence  the  time 
and  may  cause  considerable  variation. 

FAILURE  OF   EGGS   TO   HATCH. 

The  data  at  hand  are  an  insufficient  basis  for  a  definite  state- 
ment regarding  the  proportion  of  eggs  that  fail  to  hatch,  but  it 
may  be  safely  stated  that  the  number  of  failures  is  considerable. 
In  several  instances,  where  apples  containing  eggs  were  placed  in 
vessels  for  periodic  examination,  certain  of  the  eggs  failed  to  hatch. 
These  eggs  usually  remained  plump  for  several  days,  gradually 
assumed  a  yellow  color,  then  began  to  shrivel,  as  was  indicated  by  the 
minutely  convoluted  condition  of  the  shell,  and  finally  collapsed.  No 
development  of  embryo  could  be  detected  and  it  is  assumed  that  such 
eggs  were  infertile.  Some  eggs  are  destroyed,  presumably  by  insects. 
It  is  not  uncommon  to  find  egg  cavities  containing  shells  from  which  the 
contents  have  been  eaten.  It  seems  probable  also  that  some  at  least 
of  the  cavities  found  entirely  empty  had  contained  eggs  which  had  been 
removed  entire.  In  connection  with  a  test  of  egg-laying  capacity,  which 


1905.]  THE   CURCULJO   AND  THE  APPLE.  475 

will  be  recorded  in  detail  on  another  page,  record  was  made  of  the  number 
of  mature  larvae  obtained  from  a  known  number  of  eggs.  Apples,  793  in 
number,  which  contained  1,474  eggs,  deposited  at  intervals  during  a 
period  of  about  three  months,  were  examined  two  or  three  times  daily 
and  the  larvae  removed  as  they  emerged.  The  total  number  of  larvae  thus 
secured  was  1,238.  It  follows  that  236  or  16.08%  of  the  eggs  failed  to 
produce  mature  larvae.  It  is  probable  that  some  of  the  eggs  failed  to 
hatch  and  equally  probable  that  a  considerable  number  of  larvae  died  after 
leaving  the  egg.  Our  figures  then,  have  only  indirect  bearing  upon  the 
question  of  the  proportion  of  eggs  hatching,  in  showing  that  the  loss  from 
oviposition  to  maturation  of  larvae  is  in  this  case  surprisingly  small. 
But  this  work  was  under  laboratory  conditions  where  protection  was 
afforded  from  predatory  insects  and  from  adverse  weather  conditions. 
It  is  highly  probable  that  under  natural  outside  conditions  a  much 
larger  percentage  of  loss  in  the  egg  stage  would  occur. 

THE  LARVA. 

The  larva  of  the  plum  curculio  is  footless,  sluggish  in  movement, 
white  or  sometimes  yellowish  in  color,  has  a  distinct  light  brown  head, 
and  when  fully  developed  is,  as  averaged  from  measurement  of  ten 
individuals,  .32  inch  in  length  and  .078  inch  in  thickness.  The  course 
taken  by  the  larvae  on  emerging  from  the  egg  has  been  traced  in  a  number 
of  apples  and  is  found  to  be  variable.  In  one  apple  examined,  the  bore 
proceeded  straight  from  an  egg  cavity  near  the  basin  to  a  point  just 
beneath  the  skin  on  the  border  of  the  cavity ;  another  bore  was  traced 
in  a  spiral  two  and  one-half  times  around  the  fruit;  other  bores  were  found 
to  be  tortuous,  but  in  no  apple  examined  did  the  early  bore  extend  to 
the  core.  Later,  as  development  proceeds,  increased  size  is  accompanied 
by  increased  capacity  for  eating.  Apples  have  frequently  been  found 
from  which  the  pulp  had  been  entirely  eaten  out.  Early  in  the  season 
eggs  are  frequently  found  in  apples  so  small  that  it  appears  impossible 
for  larvae  to  obtain  from  them  sufficient  nourishment  for  development; 
doubtless  some  do  fail  from  this  cause  to  reach  proper  maturity;  but 
actual  trial  has  shown  that  some  very  small  apples,  if  kept  moist  and 
not  exposed  to  strong  light,  will  bring  larvae  to  full  maturity.  By  "very 
small  apples"  we  mean  such  as  are  from  one-fourth  to  three-eighths 
of  an  inch  in  transverse  diameter  and  still  thickly  covered  with  the  white 
pubescence  belonging  to  young  apples. 

No  case  has  been  found  of  the  full  development  of  a  plum  curculio 
larva  in  fruit  remaining  upon  the  trees.  It  seems  to  be  necessary  to 
larval  development  that  the  fruit  fall.  Sometimes  the  larvae  complete 
development  before  decay  of  the  fruit  begins;  more  frequently  develop- 
ment of  larvae  and  decay  go  on  together.  Badly  decayed  apples  have 
in  most  cases  furnished  the  largest  and  most  vigorous  larvae,  and  we 


476 


BULLETIN    No.  98. 


|  February. 


have  come  to  regard  the  rotten  pulp  as  the  food  most  acceptable  to 
larvae  of  the  plum  curculio. 

TIME   REQUIRED   FROM   OVIPOSITION   TO    MATURATION   OF   LARVA. 

The  length  of  time  that  the  insect  remains  in  the  fruit,  as  egg  and 
larva,  is  of  considerable  importance,  and  an  effort  has  been  made  to 
determine  this  period.  No  attempt  was  made  here  to  separate  the  egg 
stage  from  the  larval  stage,  but  simply  to  record  the  time  from  deposi- 
tion of  the  egg  to  the  full  maturity  of  the  larva;  in  other  words,  the 
time  spent  in  the  fruit.  The  work  was  carried  on  in  the  laboratory  under 
conditions  favorable  to  rapid  development  and  it  is  probable  that  the 
periods  as  recorded  may  be  a  little  shorter  than  they  would  have  been 
had  the  work  been  done  under  perfectly  natural  and  generally  less  favor- 
able conditions. 

June  22,  1903,  twenty-five  plum  curculios  were  placed  in  a  vessel 
with  three  apples.  These  apples  were  each  one  and  one-quarter  inches 
in  diameter  and  had  not  been  previously  punctured.  The  insects  had 
been  in  confinement  for  forty-eight  hours  without  food  and  were  hungry. 
The  apples  were  attacked  voraciously  and  oviposition  began  within  a 
shgrt  time.  In  forty-eight  hours  the  apples  were  removed,  placed  separ- 
ately in  numbered  vessels  and  left  undisturbed.  Larvae  emerged  as 
follows : 


July  14. 

July  15. 

July  18. 

July  20. 

July  25. 

Total. 

Apple  No.  1  

4 

2 

2 

1 

0 

9 

Apple  No.  2  

3 

1 

1 

0 

6 

11 

Apple  No.  3 

0 

0 

2 

0 

2 

4 

Days  

7 
22 

3 
23 

5 
26 

1 
'28 

8 
33 

24 

The  period  between  oviposition  and  maturation  of  larvae  here  ranges 
from  22  to  33  days,  provided  the  eggs  were  all  laid  on  the  first  day,  but, 
as  some  of  the  eggs  were  probably  laid  on  the  second  day,  the  range 
may  be  between  20  and  33  days.  The  average  time  is  26  days.  It  may 
be  noted  that  the  two  apples  which  harbored  nine  and  eleven  larvae 
respectively  were  completely  eaten  out;  nothing  remained  but  the  skin, 
the  seeds,  and  the  inedible  portion  of  the  core.  In  four  additional  cases 
in  1903,  the  exact  time  when  the  eggs  were  deposited  was  noted.  Two 
larvae  from  these  eggs  emerged  from  the  fruit  in  24  days,  one  in  25  days, 
and  one  in  27  days.  The  average  time  for  the  four  is  25  days.  During 
the  season  of  1904,  the  period  between  oviposition  and  full  development 
of  the  larvae  was  determined  under  laboratory  conditions  for  1,238  indi- 
viduals. The  first  larva  of  the  season  was  found,  emerged  from  a  fallen 
fruit,  on  June  16th.  The  first  larva  of  our  laboratory  series  emerged 
June  19th,  sixteen  days  from  deposition  of  the  egg,  June  3d.  At  the 


1905. 


THE   CURCULIO    AND  THE   APPLE. 


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other  extreme,  one  larva  emerged  September  29th, 
thirty-nine  days  from  deposition  of  the  egg,  August 
21st.  It  is  possible  and  probable  that  some  larvae 
emerged  a  few  days  earlier  than  the  one  found  on 
June  16th,  and  also  that  some  may  have  completed 
development  later  than  the  last  we  have  recorded, 
but  the  season  covered  by  definite  record  is  between 
the  dates  given  and  embraces  a  period  of  one 
hundred  and  six  days. 

The  following  tabulation  gives  the  records  obtained 
during  the  season  of  1904  on  length  of  time  in  the 
fruit. 

The  records  tabulated  are  separated  by  months 
in  order  to  show  distribution  through  the  season  and 
to  bring  out  the  fact  that  more  than  half  of  the 
larvae  came  out  of  the  fruit  during  the  month  of 
July.  The  percentages  for  each  month  are  as  follows : 

June 254  or  20.52% 

July 662  or  53. 47% 

August  272  or  21 . 97% 

September 50  or    4.04% 


1238     100.00% 

It  will  be  noted  that  there  are  a  few  precocious 
individuals  completing  the  period  in  12  and  13  days; 
also  that  there  are  some  laggards  spending  an  unus- 
ual time  in  the  fruit,  but  the  great  majority  in  all 
four  -months  emerged  within  a  comparatively  few 
days.  For  the  month  of  June,  234,  or  92.12%  of 
the  larvae  emerging  in  that  month,  came  out  in 
the  five  days,  16th  to  20th,  inclusive.  For  July,  474, 
or  71.60%  of  the  larvae  for  the  month,  came  out  in 
the  five  days,  17th  to  21st,  inclusive.  For  August, 
157,  or  57.72%,  came  out  in  the  five  days,  19th  to 
22d  and  24th;  and  in  September,  26,  or  52% 
emerged  on  the  21st,  23d,  25th,  27th,  and  29th. 
The  maximum  emergence  is.  for  June,  77  on  the 
18th  day;  July,  134  on  the  19th  day;  August,  43 
on  the  20th  day;  September,  7  on  the  21st  day. 

Considering  the  totals  for  the  season,  the  maxi- 
mum is  219  on  the  19th  day,  and  almost  90% 
emerged  on  the  days,  15th  to  23d,  inclusive.  In 


478  BULLETIN    No.  98.  [February, 

obtaining  an  average,  it  appears  that  the  period  is  shortest  early  in 
the  season  and  that  it  gradually  lengthens  as  fall  approaches.  The 
average  length  of  the  period  is  as  follows: 

In  June 18. 07  days. 

In  July 19. 15  days. 

In  August 21 . 55  days. 

In  September 26 . 00  days. 

For  the  whole  season  the  average  is  within  a  small  fraction  of  20 
days.  Without  doubt,  the  period  under  consideration  is  subject  to 
variations  from  various  causes.  Length  of  the  period  will  be  influenced 
by  weather  conditions,  by  location,  and  by  conditions  that  chance  to 
surround  the  fruit  when  it  falls;  but  the  averages  given  are  believed  to 
approximate  closely  the  normal  time  between  oviposition  and  emergence 
of  the  larvae. 

The  instinct  of  the  plum  curculio  larvae  on  emerging  from  the  apple 
is  to  bury  themselves  as  quickly  as  possible  in  the  earth.  They  may  do 
this  on  the  spot  where  they  fall,  or  they  may  crawl  several  inches,  ap- 
parently searching  for  a  suitable  place  to  enter.  Action  is  greatly 
influenced  by  time  of  day,  by  weather  conditions,  and  especially  by 
intensity  of  light.  On  bright  days,  if  not  in  very  deep  shade,  frantic 
haste  to  get  below  the  surface  is  shown;  at  evening  or  on  cloudy  days 
movement  is  more  moderate  and  time  may  be  spent  in  choosing  the 
exact  spot  for  entrance.  The  time  required  to  burrow  out  of  sight  depends 
upon  the  compactness  of  the  soil  and  varies,  according  to  our  observations, 
from  one  to  ten  minutes.  The  behavior  of  larvae  at  the  time  of  emerging 
from  the  fruit  has  been  closery  watched  on  many  occasions,  both  in  the 
orchard  and  in  the  laboratory,  and  multiplied  observations  confirm  the 
conclusion  that  exposure  to  the  open  air  is  very  distasteful  to  them ;  that 
strong  light  distresses  them;  and  that  direct  sunlight  is  very  quickly 
fatal.  It  seems  probable  that  many  larvae  emerging  in  the  daytime 
perish  from  exposure  before  they  can  burrow  beneath  the  surface.  It 
might  be  supposed  that  larvae  would  choose  night  as  the  best  time  for 
emerging,  but  apparently  time  of  day  makes  little  or  no  difference.  A 
record  obtained  in  1903  for  sixteen  larvae  gave  six  emerging  during  the 
night  and  ten  during  the  day;  of  these  latter,  five  emerged  between  the 
hours  of  10:00  A.  M.  and  1 :00  P.  M.  For  the  season  of  1904,  the  record  for 
1,238  larvae  shows  that  558,  or  45.07%  emerged  between  the  hours  of 
7:00  A.  M.  and  7:00  P.  M.,  while  680,  or  54.93%,  emerged  between  7:00 
p.  M.  and  7:00  A.  M.  Of  this  latter  number,  some,  it  is  true,  emerged  in 
early  morning  before  record  was  made,  and  between  the  hour  of  record 
and  darkness  in  the  evening,  but  we  know  that  a  very  large  portion  of 
the  number  emerged  during  the  dark  hours  of  the  night.  It  is  concluded 
from  the  observations  made  that  the  larvae  emerge  from  the  fruit  when- 


1905.]  THE   CUECULIO   AND  THE  APPLE.  479 

ever  ready,  without  making  any  distinction  with  reference  to  the  light 
conditions  prevailing  at  the  time. 

MORTALITY  AMONG  LARV^   IN  THE  FRUIT. 

It  has  been  noted  throughout  the  period  of  this  investigation  that 
there  is  a  considerable  mortality  among  larvae  while  within  the  fruit. 
Most  of  the  larvae  found  dead  in  the  burrows  were  less  than  half  grown, 
and  many  were  not  more  than  two  or  three  days  from  the  egg.  In  an 
examination  on  various  dates  of  716  fallen  apples,  169  plum  curculio 
larvae  were  found,  103  of  which  were  dead.  Here  is  an  apparent  loss  of 
nearly  61%  and,  as  many  of  the  living  larvae  were  quite  young,  it  is  pre- 
sumable that  the  percent  of  loss  would  have  been  still  further  increased. 
Reasons  for  this  mortality  have  not  been  established,  and  from  the  nature 
of  the  problem  an  actual  demonstration  would  be  extremely  difficult. 
Extended  observations  through  two  seasons  point  to  two  possible  causes. 

First — Crushing  by  growth  of  fruit.  The  writer  holds  the  opinion 
that  some  larvae  die  from  this  cause,  and  this  opinion  is  based  upon 
microscopical  examination  of-  larvae  found  dead  in  the  burrows,  and 
examination  of  the  fruit  tissue  surrounding  these  larvae.  Many  larvae 
thus  found  have  a  flattened,  crushed  appearance.  This,  taken  in  connec- 
tion with  the  fact  that  newly  formed  fruit  cells  closely  encompassed  the 
larvae  and  completely  closed  the  burrows  behind  them,  is  looked  upon  as 
fairly  good  evidence  that  death  resulted  from  pressure  from  growing  fruit 
cells.  The  eggs  of  the  plum  curculio  are  deposited  in  apples  on  the 
trees.  If  the  apples  fall  at  the  time  the  eggs  hatch  or  soon  after,  growth 
of  the  fruit  is  arrested,  and  development  of  the  larvae  may  proceed; 
but  if  the  fruit  fails  to  fall,  growth  of  tissue  continues  and  the  formation 
of  new  cells  may  be  so  rapid  and  strong  that  the  weak,  newly  hatched 
larvae  cannot  overcome  it  and  hence  are  crushed.  Additional  evidence 
that  tardy  falling  of  fruit  has  much  to  do  with  the  death  of  larvae  is  found 
in  the  records  of  larvae  developed  from  fruit  which  was  off  the  trees  at  the 
time  the  eggs  were  laid.  From  793  apples  in  which  were  deposited  1,474 
eggs,  there  emerged  1,238  fully  developed  larvae.  In  this  case,  83.92% 
of  the  eggs  deposited  resulted  in  mature  larvae.  The  loss  from  all  causes, 
including  the  possible  failure  of  some  of  the  eggs  to  hatch,  is  here  only 
16.08%,  and  it  appears  reasonable  that  this  low  percentage  of  loss  is 
largely  due  to  the  fact  that  the  newly  hatched  larvae  did  not  have  to  con- 
tend against  the  strong  growing  fruit  tissue.  It  has  been  the  accepted 
belief  for  many  years  that  the  plum  curculio  makes  the  crescent  puncture 
in  order  to  undermine  the  egg  and  thus  prevent  its  being  crushed  by 
development  of  fruit  tissue.  The  newly  hatched  larva  is  almost  as 
delicate  an  organism  as  the  egg,  and  its  resisting  power  is  exceedingly 
small,  even  though  it  can  eat  and  has  some  power  of  moving.  Probably 
it  is  the  weaker  ones  that  succumb,  but  be  that  as  it  may,  the  growth  of 
fruit  tissue  is  believed  to  be  the  real  cause  of  much  of  the  mortality  found. 


480  BULLETIN    No.  98.  {February, 

Second — The  action  of  direct  sunlight  upon  fruit.  Considerable 
evidence  has  been  gathered  tending  to  show  that  sunlight  on  fallen  apples 
is  destructive  to  the  contained  larvae.  No  living  larvae  were  found  in 
fallen  apples  that  had  been  exposed  to  the  sun  for  a  few  hours,  while 
apples  taken  from  under  the  shade  of  trees  gave  a  fair  proportion  of 
living  larvae.  This  was  tried  repeatedly  and  always  with  the  same  result. 
An  experiment  regarding  pupae  to  be  detailed  in  another  place,  may  be 
referred  to  here  as  bearing  directly  upon  this  question  of  exposure  to  sun- 
light. A  quantity  of  fallen  apples  gathered  under  trees  was  divided  into 
lots  and  placed  in  bottomless  boxes  over  earth;  in  one  box  in  the  shade 
of  a  tree  were  placed  200  apples,  in  another  in  full  exposure  to  the  sun 
were  placed  250  apples.  Conditions  surrounding  the  two  boxes  were  in 
every  way  the  same  except  in  the  matter  of  exposure  to  sun.  From  the 
earth  below  the  box  in  the  shade,  forty-two  pupae  were  taken;  from  the 
earth  below  the  exposed  box  three  pupae  were  taken.  This  last  box 
yielding  in  the  same  proportion  as  did  the  other,  should  have  yielded 
fifty-two  pupae,  but  only  three  were  found.  The  larvae  died  mostly  in 
the  fruit  and  no  reason  can  be  ascribed  other  than  the  action  of  the  sun. 
Just  how  the  action  of  the  sun  causes  death  is  not  clear.  Death  may 
result  directly  from  elevation  of  the  temperature  beyond  the  endurance 
of  the  larvae,  or  it  may  be  the  indirect  result  of  the  action  of  high  tem- 
perature upon  juices  of  the  fruit.  In  any  event,  it  is  plain  that  direct 
action  of  the  sun  is  destructive  to  larvae  in  the  fruit,  and  from  this  fact 
we  may  draw  the  practical  conclusion:  namely,  that  the  system  of 
orchard  management  that  allows  free  access  of  sunlight,  and  that  keeps  the 
ground  free  from  weeds,  so  that  the  sun  can  act  upon  fallen  fruit,  will 
be  most  helpful  in  reducing  the  number  of  these  insects. 

THE  PUPA. 

DEPTHS  TO   WHICH   LARV/E  GO   FOR   PUPATION. 

The  larvae,  following  a  natural  instinct,  go  into  the  earth  to  pupate 
and  complete  their  transformations.  How  deep  do  they  go?  This  is  a 
question  of  practical  importance  and  during  our  study  of  the  insect  con- 
siderable thought  and  much  labor  has  been  directed  towards  answering 
it  in  definite  terms.  In  searching  the  written  testimony,  we  find  apparent 
differences  of  opinion  as  to  the  depths  of  pupation.  One  writer  says 
"two  to  three  inches";  one  says  "a  few  inches";  one  "a  short  distance" ; 
two  say  "several  inches";  six  say  "  four  to  six  inches";  and  one  says 
"fifteen  to  thirty-six  inches." 

Dr.  C.  V.  Riley  (Illinois  State  Horticultural  Society,  1869,  page  84) 
says,  "When  the  grub  has  once  become  full  grown,  however,  it  forsakes 
the  fruit  it  has  ruined,  and  burrows  from  four  to  six  inches  in  the  ground," 
and  again  on  page  93  of  the  same  volume,  "Individually  I  never  found 
plum  curculio  larvae  at  a  greater  depth  below  ground  than  six  inches,  and 


1905.] 


THE   CURCULIO   AND  THE  APPLE. 


481 


my  efforts  to  find  them  in  the  winter  under  trees  from  which  infested 
fruit  had  fallen  during  the  previous  summer  have  so  far  been  fruitless." 
According  to  the  above  statements,  it  appeared  possible  to  find  pupae 
at  depths  ranging  from  two  to  thirty-six  inches,  with  possibilities  in  favor 
of  finding  the  greater  number  at  from  four  to  six  inches.  Early  in  July, 
1903,  we  began  making  excavations  under  infested  trees.  The  soil  was 
sifted  and  carefully  searched,  but  for  some  time  no  pupae  were  found,  and 
the  labor  seemed  profitless.  At  length  a  few  pupae  were  found.  This 
encouraged  further  effort  and  more  were  found.  Digging  under  trees 
finally  gave  records  of  depth  for  seventy-eight  pupae.  To  supplement 
the  digging,  to  concentrate  the  insects  and  incidentally  to  test  the  be- 
havior of  Iarv83  in  loose  as  compared  with  undisturbed  soil,  and  to  test 
the  influence  of  light  and  shade,  boxes  were  prepared  on  July  20th.  One 
box  twelve  inches  square  and  fourteen  inches  deep,  without  bottom, 
was  sunk  over  a  core  of  undisturbed  blue-grass  sod  under  the  shade  of  a 
tree  in  the  orchard.  In  this  were  placed  200  apples  gathered  from  the 
ground.  A  second  box  of  the  same  size  was  sunk  in  like  manner  in 
cultivated  soil  in  an  exposed  situation;  that  is,  not  shaded  by  trees. 
In  this  were  placed  250  apples.  A  third  box  was  set  in  an  excavation  in 
shade  under  a  tree  and  filled  with  loose  soil.  In  this  were  placed  200 
apples.  The  apples  used  were  all  picked  up  at  the  same  time  and  divided 
between  the  boxes  in  numbers  as  stated.  The  three  boxes  were  then 
covered  closely  with  cheese  cloth  and  left  undisturbed.  On  August  7th, 
the  box  over  blue-grass  sod  was  removed  and  the  core  of  earth  shaved  up. 
Pupae  to  the  number  of  forty-two  were  found  and  accurate  depth  measure- 
ments made  for  each.  The  remaining  boxes  were  lifted  and  the  earth 
examined  on  August  8th.  The  one  in  cultivated  soil  exposed  to  the  sun 
gave  three  pupa? ;  the  one  under  a  tree  in  which  loose  soil  had  been  placed 
yielded  thirty-four  pupae;  for  each  of  which  depth  record  was  made.  A 
pupa  in  its  burrow  one  inch  below  the  surface  is  shown  in  Fig.  2,  Plate  2. 
In  addition  to  the  above,  records  were  obtained  for  twenty-two  indi- 
viduals in  breeding  cages  in  the  laboratory.  Thus  in  1903  we  secured 
accurate  depth  records  for  a  total  of  179  pupse.  The  depths  as  found 
are  given  in  tabular  form  below — 


Where  found. 

No. 

Depth  in  inches. 

X 

« 

1 

1M 

1H 

1M 

2 

In  undisturbed  earth  un- 
der trees  

78 
42 
3 
34 
22 

12 
19 
1 
9 
4 

21 
15 

10 
9 

22 

7 

6 
5 

10 

1 

5 
3 

10 

2 
3 
1 

2 
1 

1 

In  earth  in  box  over  sod, 
in  shade  

In  earth  in  box  in  culti- 
vated soil  in  sun  

In    box    of   loose    soil    in 
shade  

In     earth    in    laboratory 
cages  

Totals  

179 

45 

55 

40 

19 

16 

3 

1 

482 


BULLETIN    No.  98. 


[February, 


PLVTE  2.     FIG.  1 — PLUM  CURCULIO  LARVA  IN  BURROW. 

FIG.  2 — PLUM  CURCULIO  PUPA  IN  BURROW.     x 
FIG.  3 — PLUM  CURCULIO  RESTING  POSITION. 
FIG.  4 — PLUI\T  CURCULIO   CRESCENT  PUNCTURE. 


1905.]  THE   CURCULIO  AND  THE  APPLE.  483 

The  number  at  each  depth  with  its  percentage  of  the  total  follows: 

At  a  depth  of    K  inch     45  or  25.14% 

At  a  depth  of    M  inch     55  or  30.73% 

At  a  depth  of  1  .   inch     40  or  22.35% 

At  a  depth  of  1^  inches  19  or  10.61% 

At  a  depth  of  1^  inches  16  or  8.94% 

At  a  depth  of  1%  inches    3  or  1.67% 

At  a  depth  of  2      inches    1  or  .56% 


179        100.00% 


PLATE  3.     GLASSES  USED  IN  EGG-LAYING  TEST. 

During  the  season  of  1904  depth  records  were  obtained  for  645  pupae. 
Digging  in  the  earth  under  trees  gave  twenty-four.  From  earth  in  boxes 
in  which  apples  had  been  placed,  298  records  were  obtained.  These 
boxes  were  six  in  number,  but  depth  records  were  obtained  from  only 
five  of  them.  Each  box  contained  fallen  apples  gathered  from  one  plat. 
They  were  placed  in  position  as  shown  in  Plate  4,  on  different  days 
between  July  8th  and  14th.  On  July  29th  and  30th  the  boxes  were 
lifted  and  taken  to  pieces.  The  contained  blocks  of  earth  were  then 
shaved  down  in  thin  slices  with  a  flat  knife,  and,  as  pupae  were  uncovered, 
the  depth  was  measured  and  recorded.  Measurement  was  made,  in  all 
cases,  from  the  surface  of  the  soil  to  the  bottom  of  the  burrow.  Depth 
record  for  323  individuals  was  obtained  in  the  laboratory.  Of  these, 
seventeen  were  from  a  small  box  which  had  been  filled  with  moist,  com- 
pact earth,  and  which  was  used  as  a  repository  for  surplus  larvae  that 
came  to  us  in  various  ways  and  were  not  wanted  for  other  purposes.  The 
remaining  306  records  were  obtained  from  pupae  in  tubes.  Apples  used 
in  our  test  of  egg  laying  capacity  (to  be  treated  of  in  another  place),  were 


484 


BULLETIN    No.  98. 


[  February, 


o 
I 
p 

o 


1905. 


THE   CURCULIO   AND  THE   APPLE. 


485 


PLATE  5.     Box  OF  TUBES  USED  FOR  PUPATION  RECORD. 

placed  in  jelly  glasses  such  as  are  shown  in  Plate  3,  and  as  the  larvae 
completed  their  feeding  and  emerged  from  the  fruit  they  were  placed 
separately  in  glass  tubes  one  inch  in  diameter  and  six 
inches  in  length.  These  tubes  were  prepared  by  filling  one 
end  with  earth  which  was  made  very  compact  to  the  depth  of 
one  inch ;  then  they  were  filled  with  sifted  earth  to  within  one 
and  one-half  inches  of  the  top.  This  earth  was  made  mod- 
erately firm.  As  they  received  larvae  the  tubes  were  labeled, 
covered  with  cheese  cloth,  and  placed  in  boxes  partly  filled 
with  moist  earth.  The  open  bottom  in  contact  with  moist 
earth  was  designed  to  maintain  proper  conditions  of  moisture 
throughout  the  tubes.  One  of  the  tubes  is  shown  in  Fig.  1, 
and  a  box  filled  with  tubes  in  Plate  5. 

In  the  following  tabulation  depths  are  recorded  by 
differences  of  one-fourth  inch;  totals  are  given  for  each  depth 
as  found  in  the  laboratory  and  under  outside  conditions,  with 
percentages  for  each  depth.  It  may  be  noted  that  some  of 
the  laboratory  records  show  unusual  depths.  This  is  due  to 
the  fact  that  earth  in  some  of  the  tubes  was  rather  too  dry 
FIG.  i.— Tube  and  not  sufficiently  compact.  It  appears  to  have  been  neces- 
onedpupa«oDk  sary  for  the  larvae  to  go  deeper  than  usual  in  order  to  find 

earth  sufficiently  moist  to  admit  formation  of  the  burrows. 

The  least  depth  at  which  pupae  were  found  is  one-fourth  inch  and  at 

this  depth  we  record  forty-eight.     The  extreme  depth  in  boxes,  under 

outside  conditions,  was  two  and  three-fourths  inches.     In  the  laboratory, 

eight  were  recorded  at  a  depth  of  three  inches,  one  at  three  and  one- 


486 


BULLETIN    ^o.  98. 


[February, 


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fourth  inches,  and  two  at  three  and  one-half  inches, 
but  as  already  explained  these  went  to  unusual 
depths  from  force  of  circumstances  rather  than  from 
choice. 

The  records  obtained  outside  the  laboratory  show 
315  or  97.82%  at  depths  of  two  inches  and  under,  and 
two-thirds  of  these  were  at  and  under  one  inch.  Con- 
sidering the  totals  for  the  season,  we  find  593  or 
91.94%  at  depths  of  two  inches  and  less  with  more 
than  half  or  59.29%  of  the  total  at  one  inch  and 
under.  Bringing  together  the  records  of  the  two 
seasons  we  find  the  number  and  percentages  for  each 
depth  to  be  as  follows: 


Depth  in  inches. 

Number  of  pupae. 

Percent. 

Yt 

48 

5.82 

H 

182 

22.09 

% 

155 

18.81 

i 

131 

15.90 

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69 

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93 

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VA 

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15 

1.82 

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1.46 

3 

8 

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VA 

1 

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sy2 

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824 

100.00 

The  total  number  of  records  is  824,  and  of  this 
number  772,  or  93.69%,  were  at  depths  of  two  inches 
or  less,  and  516,  or  62.62%,  were  at  depths  of  one 
inch  and  less.  From  these  figures  the  conclusion  is 
reached  that  the  great  bulk  of  the  new  generation  of 
plum  curculio  may  at  the  proper  time  be  found  as 
pupSB  very  near  the  surface.  Larvae  stop  at  the  depths 
given,  not  because  of  any  adverse  circumstances,  but 
because  of  natural  instinct.  In  our  boxes  of  loose 
soil,  out  of  doors,  larvae  had  every  opportunity  to  go 
deeper  had  their  instincts  prompted  them  to  do  so, 
but  they  went  no  deeper  than  did  the  larvae  in 
undisturbed  and  very  compact  soil.  It  is  interest- 
ing to  note  that  while  boxes  placed  in  shade  under 
trees  yielded,  respectively,  42  and  34  pupae,  the  box 
exposed  to  the  sun  yielded  only  three,  although  it 


1905.]  THE  CURCULIO  AND  THE  APPLE.  487 

contained  fifty  more  apples  than  did  either  of  the  other  boxes.  It 
appears  from  this  that  shade  is  a  more  important  factor  than  degree 
of  compactness  in  ordinary  soils.  In  this  box  exposed  to  the  sun,  most 
of  the  larvae  died  in  the  fruit  before  attaining  full  development.  Death 
was  surely  not  due  to  dryness,  for  the  apples  were  sufficiently  juicy; 
nor  to  scarcity  of  rotten  pulp,  for  most  apples  were  more  or  less 
decayed.  As  regards  conditions  likely  to  influence  larval  development 
and  emergence  from  the  fruit,  there  were  no  differences  between  the 
three  boxes  except  that  the  one  yielding  only  three  pupae  was  exposed 
to  the  sun.  The  failure  of  larvse  to  mature  under  this  exposure, 
coupled  with  the  fact,  frequently  observed,  that  larvse  are  extremely 
sensitive  to  direct  sunlight,  warrants  the  conclusion  that  the  mortality 
here  found  was  directly  due  to  the  action  of  the  sun.  If  this  is  true,  it 
follows  that  fallen  fruit  under  trees  will  have  most  of  the  contained 
larvse  killed  if  the  ground  is  clean  and  not  so  densely  shaded  as  to 
exclude  sunlight.  If  shade  is  very  dense  immediately  about  the  trees,  it 
would  be  well  to  rake  fallen  fruit  to  exposed  middles  and  thus  accom- 
plish the  same  end,  so  far  as  plum  curculio  is  concerned,  that  would 
be  attained  if  the  fruit  were  gathered  and  destroyed. 

THE   PERIOD   OF   PUPATION. 

The  period  of  pupation,  or,  more  correctly,  the  time  spent  by  the 
insects  in  the  ground,  has  been  determined  for  a  considerable  number 
of  individuals.  Record  of  time  of  entering  the  earth  was  made  for  1,724 
larvae.  Of  these,  1,264  or  73.26  percent,  emerged  as  beetles,  while  460, 
or  26.74  percent,  failed  to  come  out.  These  latter,  either  as  larvae, 
pupae,  or  beetles,  died  in  the  burrows.  Details  of  emergence  are  given 
in  the  tabulation  on  page  488. 

At  the  top  of  the  tabulation  is  given  the  number  of  days;  below  are 
given  the  records  obtained  in  1903,  followed  by  those  obtained  in  1904. 
The  latter  are  separated  into  those  obtained  from  tubes  in  the  laboratory 
and  those  obtained  from  jelly  glasses  which  were  kept  under  the  shade 
of  a  tree  in  the  orchard,  where  natural  conditions  were  more  nearly 
approximated.  The  shortest  time  recorded  is  19  days  for  one  individual. 
At  the  other  extreme,  one  beetle  emerged  48  days  from  the  time  the 
larva  entered  the  ground.  It  will  be  noted  that  all  the  very  tardy  ones, 
those  appearing  from  the  37th  to  the  48th  day,  came  from  tubes  in  the 
laboratory.  This  is  due  to  the  fact  that,  as  the  season  advanced,  the 
use  of  the  glasses  in  the  field  was  abandoned,  and  all  the  later  appear- 
ing larvae  consigned  to  the  tubes.  No  larvae  were  placed  in  glasses  after 
August  22d.  In  the  matter  of  time  in  the  ground,  we  found  no  appre- 
ciable difference  between  those  kept  in  the  laboratory  and  those  outside. 
The  long  periods  appear  to  be  a  natural  consequence  of  low  temperatures 
through  the  latter  part  of  September  and  the  month  of  October.  The 


488 


BULLETIN    No.  98. 


[February, 


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hJ      .^ 

'II1 

"c 

beetle  having  the  longest  period,  48  days, 
emerged  October  30th.  One  came  out 
November  2d,  with  a  record  of  46  days  in 
the  ground.  Some  of  the  later  larvae 
were  noted  to  be  undersized  and  evi- 
dently weaker  than  those  maturing  early 
in  the  season.  The  beetle  recorded  in 
1903  as  emerging  the  43d  day  was  from  a 
larva  so  small  and  weak  that  it  was  not 
thought  possible  for  it  to  pass  through 
the  transformations,  but  it  lived,  and  the 
beetle,  although  of  small  size,  was  other- 
wise normal. 

The  maximum  number  appearing  for 
any  one  period  was  163  the  26th  day. 
Leaving  out  of  consideration  the  very 
early  and  the  very  late  ones,  we  find 
that  the  period  from  the  22d  to  the  36th 
day,  inclusive,  covers  1,222  out  of  the 
1,264  beetles,  or  96.67%.  Computing  an 
average  time  based  on  all  the  beetles 
emerging,  we  find  that  this  average  is 
28  days. 

The  causes  of  death  in  the  460  cases 
where  larvae  failed  to  come  forth  as  living 
beetles  are  probably  several.  Some  enter 
the  ground  weak,  not  well  nourished,  and 
have  not  sufficient  vitality  to  live  through. 
Not  infrequently  the  larvae  and  pupae 
are  found  in  the  burrows,  dead  and 
thickly  covered  with  mycelial  threads  of 
fungi.  Whether  these  fungi  are  parasitic 
or  simply  saprophytic,  attacking  after 
death,  is  undetermined.  Sometimes  minute 
parts  of  larvae  or  pupae  are  found,  sug- 
gesting the  work  of  predatory  insects. 
That  larvae  often  pass  through  all  the 
transformations  and  then,  as  beetles,  die 
from  the  attacks  of  other  insects,  is  shown 
by  the  frequency  with  which  half-eaten 
beetles  are  found  in  burrows. 

Our  observations  lead  to  the  conclu- 
sion that  a  very  large  part  of  the  mor- 


1905.]  THE   CURCULIO   AND  THE  APPLE.  489 

tality  occurring  after  the  larvae  leave  the  fruit  and  before  the  beetles 
emerge  may  be  ascribed  to  insect  enemies,  and  of  these  insect  enemies 
ants  are  the  most  numerous,  active,  and  destructive.  A  small  red 
ant  and  the  common  black  ant  were  both  frequently  observed  in 
the  act  of  carrying  off  curculio  larvae  and  pupae.  An  effort  to  ascertain 
the  number  of  larvae  obtainable  from  a  known  number  of  punctured 
apples  was  seriously  interfered  with  because  ants  carried  off  the  larvae 
as  fast  as  they  emerged,  and  in  our  outside  pupating  boxes  we  are  confi- 
dent that  the  number  of  pupae  found  would  have  been  very  much  greater 
had  it  been  possible  to  exclude  the  ants.  Ten  pupae  placed  in  the  center 
of  the  cloth  cover  of  a  box  which  projected  four  inches  above  the  ground 
surface  were  discovered  by  ants,  killed,  and  removed  from  the  box  within 
thirty  minutes.  Other  similar  tests  all  serve  to  show  that  ants  have  great 
capacity  for  the  destruction  of  curculio  larvae  and  pupae. 

THE  BURROWS. 

The  burrows  in  which  pupae  are  found  are  oval  in  form,  with  smooth 
walls,  and  are  not  lined  with  web- work.  They  are  made  by  the  larvae, 
probably,  as  Riley  suggests,  "by  turning  round  and  round  until  the 
right  size  and  degree  of  smoothness  is  attained."*  A  larva  in  its  burrow 
one  inch  below  the  surface  is  shown  in  Fig.  1,  Plate  2.  The  burrows  are 
oblique  to  the  surface  and  the  pupae  always  rest  with  the  head  up.  No 
record  was  obtained  of  the  time  spent  in  pupa  form,  but  it  surely  is 
several  days  shorter  than  the  period  spent  in  the  earth.  Probably  two 
or  three  days  may  be  required  by  the  larvae  after  entering  the  earth, 
before  they  change  to  pupae,  and,  at  the  end  of  the  pupa  stage,  two  or 
three  days  elapse  between  the  casting  of  the  pupa  skin  and  the  emergence 
of  the  beetle.  Beetles  fresh  from  the  pupa  stage  are  reddish  in  color 
and  quite  soft-bodied.  It  required  a  few  days  to  assume  natural  colors 
and  attain  sufficient  hardness  of  body  to  enable  them  to  reach  the  surface. 
Newly  emerged  beetles  have  a  bright,  fresh  appearance  that  serves  to 
distinguish  them  from  those  that  have  hibernated. 

THE  FULL  PERIOD  FROM  DEPOSITION  OF  THE  EGG  TO  THE  EMERGENCE  OF  THE 

MATURE  BEETLE. 

The  life  cycle  of  the  plum  curculio,  or  the  period  from  deposition 
of  the  egg  to  the  emergence  of  the  mature  beetle,  as  observed  in  this 
investigation,  may  have  an  extreme  range  of  from  31  to  90  days,  by 
adding  the  shortest  period  in  the  fruit  to  the  shortest  observed  period 
in  the  ground  for  the  minimum  and  adding  the  other  extremes  in  the 
same  way  for  the  maximum.  But  a  long  period  in  the  earth  is  not 
necessarily  preceded  by  a  long  period  in  the  fruit,  nor  is  a  long  period 
in  the  fruit  usually  followed  by  an  abnormal  period  in  the  earth.  It 

*Transactions  Illinois  Horticultural  Society,  1869,  page  84. 


490  BULLETIN    No.  98.  [February, 

is  not  probable  that  any  curculio  completed  the  life  cycle  in  the  mimi- 
mum  time  of  31  days,  or  that  any  required  the  extreme  time  of  90  days. 
As  a  matter  of  fact,  the  beetle  recorded  as  emerging  in  48  days,  had  a 
period  in  the  fruit  as  egg  and  larva  of  only  24  days,  making  the 
whole  period  from  oviposition  to  final  emergence  only  72  days.  One 
curculio  recorded  as  emerging  on  the  41st  day  has  a  record  of  only  20 
days  in  the  fruit,  making  the  full  time  61  days.  The  average  time  in 
the  fruit,  20  days,  added  to  the  average  time  in  the  ground,  28  days, 
gives  an  average  time  from  oviposition  to  emergence  of  the  beetle  of  48 
days,  and  the  great  majority  of  the  individuals  for  which  we  have  record 
will  come  within  a  few  days,  one  way  or  the  other,  of  this  average. 

BETWEEN   WHAT   DATES   ARE  MOST   PUP^E    IN   THE   EARTH? 

From  what  has  preceded  regarding  depth  for  pupation  and  time 
spent  in  the  ground,  it  appears  that  the  new  generation  of  the  plum 
curculio  is  in  the  earth,  mostly  within  two  inches  of  the  surface,  for  a 
period  of  about  four  weeks  during  the  summer.  If  all  eggs  were  laid 
on  the  same  day,  or  within  a  few  days  of  each  other,  so  that  the  whole 
crop  for  the  season  would  be  in  the  ground  at  the  same  time,  the  problem 
of  control  by  attack  during  pupation  would  be  greatly  simplified;  but, 
unfortunately,  the  period  for  depositing  eggs  is  greatly  prolonged,  as 
has  been  shown.  It  follows  that  beetles  of  the  new  generation  come 
from  the  earth  and  are  at  work  on  the  fruit  long  before  the  older  genera- 
tion has  ceased  laying  eggs.  While  our  records  show  a  period  of  143 
days  between  June  17th,  when  the  first  larva  entered  the  ground,  and 
November  7th,  when  the  last  beetle  emerged,  there  must  be  some  shorter 
period  that,  while  not  including  the  precocious  individuals  nor  the 
laggards,  would  cover  a  great  majority  of  the  insects.  Commencing 
with  July  17th,  the  day  of  the  first  emergence  of  beetles,  let  us  consider 
a  period  of  30  days,  which  would  include  August  15th.  Up  to  this  last 
date,  1,536,  or  90%,  of  our  1,700  larvae  had  entered  the  ground;  but 
the  time  between  June  17th,  when  the  first  larva  entered  the  ground, 
and  the  emergence  of  the  first  beetle,  on  July  17th,  is  29  days,  one  day 
more  than  the  average  time  spent  in  the  ground;  and,  as  many  beetles 
emerged  in  less  than  the  average  time,  a  considerable  number  would 
likely  escape  before  July  17th.  To  guard  against  this,  we  will  shift 
the  thirty-day  period  and  consider  it  as  extending  from  July  10th  to 
August  8th.  There  have  entered  the  ground  up  to  this  last  date  1,479, 
or  87%,  of  the  total  number  of  larvae,  and  the  number  likely  to  emerge 
and  escape  before  July  10th  would  be  very  small.  If  we  make  the 
period  40  days,  and  extend  the  time  to  include  August  18th,  we  have 
1,565,  or  92.06%,  of  the  1,700  larvae  in  the  ground.  Lengthen  the 
time  still  further  to  include  the  whole  month  of  August,  a  period  of  53 
days,  and  we  cover  1,645,  or  96.76%,  of  larvae  entering  the  ground. 


1905.]  THE  CURCULIO  AND  THE  APPLE.  491 

For  this  season  of  1904,  the  date  for  commencing  operations  against 
the  curculio  in  the  ground  may  be  given  as  July  10th.  The  percentage 
of  the  crop  controlled  or  destroyed  would  then  depend  upon  how  long 
work  was  continued,  with  .probabilities  that  operations  extended  over 
thirty  days  would  affect  87%,  forty  days,  92%,  and  fifty-three  days, 
nearly  97%  of  the  curculio  crop.  The  date  given  for  commencing  work 
applies  only  to  the  one  season  of  1904.  It  must  be  moved  one  way  or 
the  other  according  as  the  season  is  late  or  early.  In  relation  to  the 
date  of  full  bloom,  which  for  1904  occurred  on  May  10th,  our  date  of  July 
10th  comes  sixty-one  days  later.  In  1903  the  date  of  full  bloom  was 
April  22d.  Adding  sixty-one  days,  the  date  for  commencing  would  fall 
on  June  22d,  eighteen  days  earlier  than  for  1904. 

It  is  not  intended  to  convey  the  idea  that  there  is  a  positive  relation 
between  the  blooming  period  and  curculio  pupation;  other  factors  may 
intervene  to  vary  the  time,  but  in  a  general  way  the  period  of  full  bloom 
may  serve  as  a  ba'sis  from  which  to  calculate.  The  dates  given  above 
as  possible  limits  to  the  period  during  which  effort  may  be  directed 
against  curculio  in  the  ground,  are  intended  to  be  only  approximate, 
but  they  have  been  named  only  after  careful  study  of  the  situation  as 
found  in  central  Illinois  during  the  last  two  seasons,  and  are  believed 
to  be  as  nearly  correct  as  it  is  possible  to  make  them  with  the  informa- 
tion at  hand.  In  the  northern  part  of  the  state  they  would  vary  but  little, 
but  in  the  south,  where  egg  laying  begins  earlier,  the  period  would  begin 
from  ten  to  fifteen  days  earlier.  To  definitely  establish  this  period  is 
important  in  connection  with  the  treatment  to  be  given.  This  treat- 
ment will  be  suggested  in  considering  means  of  repression. 

THE  BEETLE  FROM  EMERGENCE  TO  HIBERNATION. 

Emergence  of  plum  curculio  beetles  is  governed  in  great  part  by 
weather  conditions.  Dryness  of  the  soil  retards  movement  to  the  surface, 
and  without  doubt  extreme  drouth  proves  fatal  to  many,  either  in  the 
pupa  state  or  at  the  time  of  transformation  to  beetles.  A  shower  brings 
the  beetles  out  in  great  numbers,  and,  in  general,  moist  conditions  of 
soil  are  favorable  to  emergence.  Precocious  individuals,  developed  from 
the  first  eggs  deposited,  began  to  emerge  as  beetles  on  July  16th;  but 
the  earliest  to  appear  among  those  under  control  in  the  laboratory  came 
out  on  July  17th.  From  this  date,  beetles  continued  to  emerge  through- 
out the  summer  and  until  late  in  the  fall.  With  July  17th  as  the  earliest 
date  of  emergence,  and  November  7th  as  the  date  of  the  last  emergence, 
we  have  a  period  of  114  days  during  which  beetles  may  emerge.  It  is 
an  interesting  coincidence  that  the  period  during  which  larvae  entered 
the  ground  is  exactly  the  same  as  the  period  during  which  beetles 
emerged,  114  days.  The  first  larva  entered  the  ground  on  June  17th; 


492  BULLETIN    No.  98.  [February, 

the  last  on  October  9th.  There  are  twenty-nine  days  between  the  entrance 
of  the  first  larva  and  the  emergence  of  the  first  beetle,  and  also  twenty- 
nine  days  between  the  entrance  of  the  last  larva  and  the  emergence  of 
the  last  beetle.  But  this  is  merely  a  coincidence,  and  has  no  bearing 
upon  individual  periods  in  the  ground,  as  is  shown  by  the  fact  that, 
while  1,039  larvae,  or  61.11%,  of  the  total  number  entered  the  ground 
during  the  first  twenty-nine  days,  or  before  any  beetles  emerged,  only 
twenty-nine,  or  2.28%,  of  the  beetles  emerging  came  out  during  the 
last  twenty-nine  days,  or  after  the  last  larva  entered  the  ground.  The 
maximum  number  emerging  on  any  one  day  was  ninety-one  on  July 
27th.  The  number  emerging  by  months  is  as  follows: 


Month  . 

Number  . 

Percent  . 

July 
August 
September 
October 
November 

592 
449 
188 
34 
5 

46.69 
35.41 
14.83 
2.68 
.39 

1268 

1(10.00 

Newly  emerged  beetles  usually  remain  quiet  for  a  time,  apparently 
to  allow  complete  hardening  of  the  body  wall  and  appendages.  Then 
they  seek  the  food  plants  and,  so  far  as  the  evidence  at  hand  indicates, 
spend  the  rest  of  the  season  in  eating  and  sleeping. 

Beetles  that  came  from  the  earth  early  in  the  season  were  kept  in 
cages  and  supplied  at  frequent  intervals  with  fresh  apples.  They  ate 
voraciously,  but  did  not  breed  and  no  eggs  were  laid.  Early  writers 
held  diverse  opinions  as  to  the  number  of  broods  of  the  plum  curculio, 
and  the  question  was  much  discussed  until  1870,  when  Riley,  by  careful 
experiments,  established  the  fact  that  there  is  but  one  brood.  In  the 
Transactions  of  the  Illinois  Horticultural  Society  for  1870,  Riley  says: 
"But  as  there  seem  to  be  exceptions  to  all  rules,  so  there  are  to  this;  yet 
the  exceptions  are  just  about  sufficient  to  prove  the  rule,  for  as  far  south 
as  St.  Louis,  not  more  than  one  percent  of  the  beetles  lay  any  eggs  at  all, 
until  they  have  lived  through  one  winter;  or  in  other  words,  when  one 
female  will  pair  and  deposit  a  few  eggs  the  same  summer  she  was  bred, 
ninety-nine  will  live  on  for  nearly  ten  months  and  not  deposit  until  the 
following  spring.  In  more  northern  latitudes  I  doubt  if  any  exceptions 
to  the  rule  will  be  found."  Eating  is  the  principal  business  of  the  beetles 
from  the  time  they  emerge  until  the  fruit  is  gone,  and  it  is  during  this 
period  in  late  summer  and  fall  that  the  greatest  amount  of  injury  to 
apples  is  done.  Feeding  punctures  made  early  in  the  season,  or  during 
May  and  June  are  usually  small;  simply  shallow  cylindrical  holes  that 
commonly  are  nearly  obliterated  by  the  later  growth  of  the  apple,  so  that 
eventually  they  constitute  but  slight  surface  blemishes.  The  later 
punctures  are  larger  and  remain  as  permanent  blemishes,  destroying  the 


190.r).]  THE   CURCULIO   AND  THE  APPLE.  493 

• 

value  of  the  fruit.  The  character  of  these  late  punctures  is  shown  in 
Plate  19.  Not  only  are  the  cylindrical  cavities  somewhat  deeper  and 
larger,  but  they  are  further  enlarged  by  excavation  back  beneath  the  skin 
as  far  as  the  length  of  the  beak  will  allow.  When  completed,  the  opening 
through  the  skin  may  be  about  one-sixteenth  of  an  inch  in  diameter, 
while  the  cavity  in  the  pulp  below  may  be  one-fourth  of  an  inch  across 
and  one-eighth  of  an  inch  deep.  As  evaporation  takes  place,  the  skin  that 
has  been  undermined  shrinks  back,  thus  enlarging  the  opening.  It  also 
becomes  discolored,  appearing  as  a  dark  brown  ring  about  the  opening. 


PLATE  6.     APPLE  SHOWING  COLLAPSED  AREA. 

Not  infrequently  excavations  are  so  numerous  that  several  run  together 
causing  the  surface  of  a  considerable  area  to  collapse,  working  utter 
ruin  to  the  fruit.  Plate  6  is  from  a  photograph  of  an  apple  affected  in 
this  manner.  There  are  twenty-one  punctures  on  the  surface  shown; 
thirteen  of  these  were  so  excavated  that  they  ran  together  undermining 
the  skin ;  as  a  consequence  the  surface  collapsed. 

For  additional  data  on  the  feeding  habits  of  newly  emerged  beetles, 
ten  were  placed  separately  in  glasses  as  they  came  from  the  earth,  on 
August  26th,  and  supplied  with  apples.  Five  of  these  were  given  fresh 
apples  daily  for  fifty-one  days,  or  until  October  21st,  and  as  apples  were 
removed  record  was  made  of  the  punctures.  The  remaining  five  were 
given  fresh  apples  about  once  each  week  for  the  same  period  and  similar 
record  made  from  the  fruit  removed. 

Those  supplied  with  fresh  apples  daily  gave  the  following  record: — 


494 


BULLETIN    No.  98. 


[February, 


Number  of  beetle  

1 

2 

3 

4 

8 

Total  punctures  made  

35 

8 

4P 

68 

7?, 

Number  of  days  on  which  punctures  were  made  
Number  of  days  on  which  no  punctures  were  made  .... 
Greatest  number  of  punctures  made  in  one  day  

24 

27 
6 

5 
40 
3 

30 

21 
5 

32 
19 

7 

32 

19 

4 

No.  2  made  only  eight  punctures  and  died  on  the  forty-fifth  day. 
With  the  others,  there  were  periods  of  from  three  to  seven  days  during 
which  no  punctures  were  made.  With  all,  the  number  of  punctures 
diminished  as  the  season  advanced,  and  few  were  made  during  the  last 
two  weeks  of  the  period.  The  five  examined  at  less  frequent  intervals 
gave  the  following  record: — 


Number 
of 
beetle. 

Dates  when  record  was  made. 

Total. 

Sept.  2. 

Sept.  9. 

Sept.  16. 

Sept.  23. 

Oct.  3. 

Oct.  10. 

Oct.  21. 

1 
2 
3 
4 
5 

8 
22 
24 
21 
20 

7 
19 
7 
9 

7 
8 
19 
5 
3 

5 
6 
11 
2 
5 

3 
20 

24 
8 

7 

2 
5 

3 

9 
4 
4 

28 
63 
111 

47 
48 

This  record  discloses  marked  individual  differences  in  the  number  of 
punctures.  The  beetles  also  differed  in  general  activity.  Some  seemed 
content  to  lie  for  days  at  a  time  with  the  appendages  drawn  close  to  the 
body ;  others,  even  when  not  feeding  were  moving  about  much  of  the  time 
and  rested  for  short  periods  only. 

From  about  the  middle  of  August  as  long  as  the  apples  remained  upon 
the  trees,  the  beetles  used  these  excavations,  to  a  considerable  extent,  as 
resting-places,  spending  the  time  when  not  feeding  safely  housed  and 
often  entirely  hidden  from  view.  In  the  summer  of  1903,  beetles  were 
first  taken  from  cavities  on  August  llth.  Frequently  beetles  fed  from 
the  interior  of  these  cavities,  often  increasing  the  size  of  the  excavation 
to  three  or  four  times  the  size  attained  by  work  from  the  outside. 

Of  fifty-four  beetles  taken  from  fruits,  August  21  and  22,  1903, 
thirty-two,  or  59.26%,  were  in  cavities,  while  twenty-two,  or  40.74%, 
were  on  the  outside  of  the  fruits.  Of  forty-five  taken  October  1st  and 
2d,  38,  or  84.44%,  were  in  cavaties,  and  7,  or  15.56%,  were  on  the 
outside.  As  the  season  advanced,  the  tendency  to  hide  in  the  cavities 
increased  greatly.  In  two  cases  beetles  were  found  in  cavities  of  fallen 
fruit,  but  those  above  recorded  were  all  in  apples  upon  the  trees.  Cur- 
culios  found  in  cavities  do  riot  willingly  leave  them.  Jarring  appar- 
ently does  not  disturb  them,  and  often  they  will  not  move  at  all  until 
forced  to.  They  rest  with  legs  drawn  close  up  to  the  body  and  will 
remain  for  hours  without  sign  of  life.  As  many  as  four  have  been 
taken  from  a  single  cavity. 

As  the  fall  temperatures  get  lower  the  beetles  become  less  and  less 


1905.]  THE   CUKCULIO   AND  THE  APPLE.  495 

active.  Finally  they  leave  the  trees  and  seek  places  to  hibernate.  The 
place  most  commonly  chosen  for  hibernation  is  on  or  very  near  the  ground 
under  grass,  or  such  other  rubbish  as  may  be  present.  It  is  recorded 
that  they  also  hibernate,  "under  the  rough  bark  of  both  fruit  and  forest 
trees  and  under  the  shingles  of  houses."  Diligent  search  for  the  beetles 
among  grass  and  weeds  under  orchard  trees  was  made  in  November,  1902, 
in  March,  1903,  and  again  in  November  of  the  same  year,  and  several, 
specimens  were  taken,  all  of  them  under  dead  grass  in  immediate  eon- 
tact  with  the  earth.  Search  was  also  made  in  woods  adjoining  an  or- 
chard, but  no  beetles  could  be  found. 

That  they  do  hibernate  in  woods,  however,  seems  at  least  very  probable 
because  it  is  so  universally  the  case  that  orchards  in  close  proximity  to 
woodlands  are  most  infested  in  those  portions  nearest  the  woods.  The 
difference  in  infestation,  between  parts  of  the  orchard  near  and  those 
remote  from  woods,  is  most  marked  in  cultivated  orchards.  When  kept 
free  from  weeds  and  grass,  orchards  do  not  offer  so  good  shelter  for 
hibernating  insects.  They  are  naturally  driven  to  seek  shelter  else- 
where and  woods  afford  ample  opportunities  for  secure  shelter. 

When  orchards  are  not  cultivated,  as  is  the  case  with  many  in  Pike 
County,  the  work  of  the  plum  curculio  is  more  evenly  distributed  over  the 
orchard,  but  even  here  the  fruit  on  rows  adjoining  bodies  of  timber  gener- 
ally shows  greater  injury  than  does  the  fruit  on  trees  further  away. 

THE  BEETLE  IN  SPRING. 

In  the  spring  of  1903  the  earliest  search  for  hibernating  curculios 
was  made  on  March  31st;  nearly  the  whole  day  was  given  to  the  work, 
but  no  beetles  were  found.  Search  was  again  made  on  April  14th,  and 
at  intervals  up  to  April  27th,  on  which  date  the  first  beetles  were  dis- 
covered. Only  a  few  specimens  were  secured  and  these  were  found,  as 
were  those  found  in  the  fall,  in  contact  with  the  ground  under  dead  grass. 
In  view  of  the  abundance  of  the  insect  in  1902,  it  was  disappointing  to 
meet  with  such  ill  success  in  finding  the  hibernating  beetles,  because 
more  detailed  information  is  desired  regarding  hibernating  habits  and 
situations  most  chosen.  To  be  sure  the  area  available  for  hibernating 
was  large,  and  the  area  actually  searched  in  detail  small,  but  it  seemed 
reasonable  to  expect  to  find  more  than  were  found.  However,  the 
beetles  were  present  somewhere,  as  was  shown  by  their  abundance  on  the 
trees  a  month  later.  So  far  as  found,  the  beetles  were  single;  appar- 
ently they  are  not  gregarious  in  hibernating.  During  the  spring,  the 
trees  were  carefully  searched  at  frequent  intervals,  with  a  view  to  ascer- 
taining when  the  beetles  first  went  into  them,  but  no  beetles  were  found 
on  the  trees  until  May  10th.  They  appeared  to  come  all  at  once.  None 
could  be  found  on  the  trees  May  9th,  but  May  10th  they  were  abundant. 
Apple  buds  began  opening  April  16th.  Trees  were  in  full  bloom  April 


496  BULLETIN    No.  98.  [February, 

22d,  and  the  petals  had  practically  all  fallen  by  May  4th.  It  was,  then, 
one  week  after  the  end  of  the  blooming  period  when  beetles  were  first 
found  upon  the  trees.  The  apples  had  at  that  time  begun  to  form,  and 
some  could  be  found  that  were  one-fourth  of  an  inch  in  diameter. 

In  the  spring  of  1904,  attempts  were  again  made  to  locate  the  beetles 
in  hibernating  quarters,  and  to  ascertain  the  date  of  first  appearance 
on  the  trees,  but  no  new  information  was  secured  regarding  hibernating 
quarters,  as  no  beetles  could  be  found.  The  first  curculio  of  the  season 
was  taken  by  Mr.  J.  R.  Shinn  from  a  cluster  of  blossom  buds  on  a  Siberian 
crab  tree  near  a  dwelling,  April  30th.  April  28th,  the  systematic  shaking 
of  selected  apples  trees  was  commenced.  A  sheet  twenty-four  feet  square 
was  spread  under  the  trees  from  one  to  three  times  daily.  The  trees  were 
jarred  and  shaken  and  record  made  of  the  curculios  captured.  Tree 
No.  1  was  located  at  the  southwest  corner  of  the  orchard  adjoining  a 
tract  of  woodland.  Tree  No.  2  was  located  diagonally  across  the  orchard 
near  the  northeast  corner.  Other  trees  in  the  body  of  the  orchard  were 
shaken  frequently,  but  with  less  regularity.  The  first  curculio  secured 
in  this  way  was  taken  from  tree  No.  1  the  evening  of  May  4th.  Others 
from  the  same  tree  were  taken  as  follows — one,  May  5th;  five,  May  7th; 
one,  May  10th;  one,  May  12th;  two,  May  13th;  one,  May  15th;  one, 
May  18th;  and  three,  May  19th.  From  tree  No.  2,  the  first  curculio  was 
taken  May  17th  followed  by  one  May  18th.  The  first  from  other  trees 
was  taken  May  7th,  followed  by  captures  of  one,  two,  and  three  at  inter- 
vals during  the  month.  From  our  records,  it  appears  that  beetles  were 
taken  from  trees  six  days  earlier  in  1904  than  in  1903.  Gauged  by 
blooming  dates,  the  appearance  of  the  beetles  upon  trees  was  fully  two 
weeks  earlier  this  season  than  last.  Apple  buds  in  1904  began  bursting 
about  May  3d.  Trees  were  in  full  bloom  May  10th,  and  the  petals  had 
practically  all  fallen  by  May  15th. 

The  date  of  the  iirst  appearance  of  the  beetles  in  spring,  and  their 
feeding  habits  previous  to  the  setting  of  fruit  are  matters  of  importance 
because  they  bear  directly  upon  the  early  application  of  insecticides. 
If  the  beetles  feed  freely  upon  buds,  young  leaves,  and  flowers,  early 
spraying  should  kill  many  of  them. 

In  the  eleventh  report  of  the  State  Entomologist  of  New  York  for 
1895,  page  122,  Dr.  Lintner  says:  "The  Plum  Curculio  (Conotrachelus 
nenuphar}  enters  upon  the  scene  at  least  two  weeks  before  its  first  cres- 
cent cuts  are  made  in  the  fruit,  ready  and  free  to  devote  all  its  energies 
to  obtaining  the  supply  of  food  needed  for  the  development  of  its  eggs 
and  for  the  labors  attending  its  complicated  and  painstaking  method  of 
oviposition."  Dr.  Riley  gives  his  testimony  as  to  early  appearance  as 
follows:  "In  central  Illinois  and  in  central  Missouri  the  beetles  may  be 
found  in  the  trees  during  the  last  half  of  April,  but  in  the  extreme  southern 
part  of  Illinois  they  appear  about  two  weeks  earlier,  while  in  the  extreme 


1905.]  THE  CURCULIO   AND  THE  APPLE.  497 

northern  part  of  the  same  state  they  are  fully  two  weeks  later.  Thus, 
in  the  single  State  of  Illinois,  there  is  a  difference  of  about  a  month  in 
the  time  of  the  curculio's  first  appearance  on  your  fruit  trees;  and  I 
need  hardly  remind  you  that  the  time  will  vary  with  the  forwardness  or 
lateness  of  the  season.  As  we  shall  see  from  the  sequel,  it  is  very  im- 
portant that  we  know  just  when  first  to  expect  Mrs.  Turk,  and  I,  there- 
fore, lay  it  down  as  a  rule  applicable  to  any  latitude,  that  she  commences 
to  puncture  peaches  when  they  are  the  size  of  small  marbles  or  of  hazel- 
nuts,  though  she  may  be  found  on  your  trees  as  soon  as  they  are  in 
blossom."*  There  are  other  writers  giving  like  testimony  regarding  the 
early  appearance  of  beetles  upon  the  trees.  I  am  not  aware  of  any 
peculiar  conditions  tending  to  retard  the  appearance  of  beetles  upon  the 
trees,  either  in  the  spring  of  1903  or  in  1904,  in  Pike  County,  where  our 
observations  were  made;  but  we  utterly  failed  to  find  any  trace  of  them 
upon  the  trees  previous  to  May  10  in  1903,  and  "May  4  in  1904.  After 
May  10  in  1903,  beetles  were  found  on  branches,  twigs,  leaves,  and 
fruit  without  trouble.  If  they  were  there  before,  they  certainly  eluded 
diligent  and  persistent  search.  Regarding  spring  feeding  habits  of  the 
beetles,  it  has  been  demonstrated  by  several  experimenters  that  they  will 
accept  leaves  and  the  leafy  parts  of  flowers,  as  well  as  fruits.  Dr.  Forbes 
in  1888  and  1889  foundf  that  beetles  confined  with  plum  leaves  made 
excavations  in  midribs  and  petioles ;  supplied  with  fruit  and  leaves,  both 
were  eaten;  the  fruit  perhaps  the  more  freely.  As  between  leaves  and 
blossoms,  the  beetles  showed  preference  for  the  latter,  eating  the  leafy 
parts.  Given  roses  in  bloom,  the  petals  and  later  the  calyx  and  pe- 
duncle were  eaten,  and  they  also  fed  upon  the  flowers  of  the  honey- 
suckle and  snowball. 

In  our  work  during  the  two  seasons,  it  has  been  found  that  beetles 
confined  with  fresh  apple  leaves  fed  upon  these  leaves  very  sparingly ; 
supplied  with  both  leaves  and  fruit,  only  an  occasional  small  puncture 
was  made  on  midribs  and  petioles  of  leaves  while  the  fruit  was  freely 
punctured.  It  has,  however,  been  frequently  noted  that  beetles  feed 
upon  the  stems  of  apples  to  some  extent.  When  pairs  have  been  con- 
fined with  apples,  the  male  has  been  observed  puncturing  the  stem  while 
the  female  was  ovipositing  upon  the  apple,  and  it  has  been  thought  pos- 
sible that  this  was  the  exercise  of  an  instinct  operating  to  insure  the  fall 
of  the  apple,  but  examination  of  a  large  number  of  apples  has  failed 
to  bring  to  light  anything  in  support  of  this  idea. 

All  records  consulted  that  bear  upon  this  matter  of  early  feeding 
deal  with  beetles  in  confinement;  no  reference  to  observations  made 
upon  the  work  of  free  insects,  in  the  trees,  has  been  found.  It  is  a  per- 
fectly natural  inference  that  insects  when  free  will  feed  the  same  as  when 

*The  American  Entomologist,  2:  130,  1870. 

|17th  Report  State  Entomologist,  Illinois,  for  1889-1890,  pages  21,  22  (1891). 


498  BULLETIN    No.  98.  [February, 

confined;  direct  evidence,  however,  would  be  desirable.  Prolonged 
search  for  such  evidence  has  been  made,  but  none  has  been  found.  In 
1903,  fruits  had  commenced  development  before  any  beetles  were  found 
in  the  trees;  from  the  time  the  beetles  were  found  they  worked  indus- 
triously, but  so  far  as  our  observations  went  the  work  was  confined 
entirely  to  apples.  No  puncturing  of  leaves  or  twigs  was  discovered, 
although  beetles  were  frequently  found  resting  upon  both  twigs  and 
leaves. 

Actual  demonstration  of  the  use  of  succulent  parts  for  food  before 
the  fruit  was  formed,  would  point  to  the  early  application  of  some  insect- 
icide as  a  possible  effective  means  of  reducing  the  number  of  beetles, 
but  thus  far  we  have  failed  to  secure  evidence  warranting  a  recommenda- 
tion of  spraying  for  this  particular  purpose. 

In  1903;  after  May  10th,  the  date  of  the  first  appearance  of  the 
beetles,  feeding  punctures  on  apples  multiplied  rapidly  and  crescent 
punctures  became  daily  more  numerous.  Fruits  at  this  time  had  but 
just  begun  to  enlarge  and  many  were  very  small.  Apples  less  than 
one-fourth  of  an  inch  in  diameter  frequently  were  marked  with  two  or 
three  crescents  and  as  many  cylindrical  feeding  punctures.  These  apples 
were  thickly  covered  with  the  normal  white  pubescence,  and  all  exam- 
inations of  punctures  were  of  necessity  made  under  a  lens.  Three  or 
four  days  after  puncturing  began,  apples  began  to  fall  hi  considerable 
numbers.  Whether  this  was  directly  attributable  to  the  work  of  the 
curculio  or  not,  has  not  been  determined.  Many  early  punctured  fruits 
persisted  until  well  into  the  summer,  and  some  remained  on  the  trees 
through  the  season,  but  practically  all  the  fruit  that  fell  was  more  or  less 
punctured.  It  is  expected  that  a  certain  portion  of  very  young  fruits 
will  fall,  either  because  of  imperfect  fertilization,  unfavorable  weather 
conditions,  or  some  cause  outside  of  insect  work;  so  that  it  is  not  possible 
to  ascribe  the  drop  here  referred  to  wholly  to  the  action  of  curculio. 

OVIPOSITION. 

Mating  begins  soon  after  the  beetles  come  from  their  hibernating 
quarters,  and  deposition  of  eggs  by  what  Dr.  Lintner  refers  to  as  "its 
complicated  and  painstaking  method  of  oviposition,"  follows  soon  after. 
The  beetles  do  not  wait  for  the  apple  to  develop,  but  begin  almost  as 
soon  as  the  petals  have  fallen.  The  procedure  in  oviposition  is  a  matter 
of  no  great  practical  importance,  but  cannot  help  being  of  great  interest 
to  any  student  of  insect  habits  and  instincts.  It  is  only  a  detail  in  the 
life  of  the  insect,  but  the  observer  sees  in  it  some  importance,  because 
it  exemplifies  that  principle  of  scientific  investigation  which  demands  for 
it  the  same  accurate  observation  and  clear  expression  that  would  be 
accorded  larger  and  more  general  matters.  It  should  be  borne  in  mind 
that  each  detail  is  but  a  link  in  the  chain  that  makes  possible  the  deduc- 


1905.]  THE   CURCULIO   AND  THE  APPLE.  499 

tion  of  a  right  conclusion  or  the  broad  statement  of  fact  or  principle. 
I  have  before  me  statements  of  this  process  of  oviposition  compiled  from 
twenty-two  different  writers.  These  statements  exhibit  considerable 
variation  in  method  of  work  and  in  sequence  of  acts,  and  the  question 
naturally  arises,  how  many  of  these  statements  are  founded  upon  actual 
observation?  Some  surely  are  so  founded,  others  leave  one  in  doubt, 
and  still  others  are  quite  evidently  repeated  from  some  printed  source. 
Below  are  eight  of  the  twenty-two  statements,  numbered  as  in  my  list. 

1.  "As  soon  as  the  plums  are  the  size  of  peas,  the  weevil  commences 
the  work  of  destruction  by  making  a  semi-circular  cut  through  the  skin 
with  her  long,  curved  snout,  in  the  apex  of  which  cut  she  deposits  a  single 
egg." 

2.  "In  doing  this,  the  beetle  first  makes  a  small,  crescent-shaped 
incision  with  its  snout  in  the  skin  of  the  plum,  and  then,  turning  round, 
inserts  an  egg  in  the  wound." 

3.  "Having  taken  a  strong  hold  of  the  fruit,  the  female  makes  a 
minute  cut  with  the  jaws,  which  are  at  the  end  of  her  snout,  just  through 
the  skin  of  the  fruit,  and  then  runs  the  snout  under  the  skin  to  the  depth 
of  one-sixteenth  of  an  inch,  and  moves  it  back  and  forth  until  the  cavity 
is  large  enough  to  receive  the  egg  it  is  to  retain.     She  next  changes  her 
position  and  drops  an  egg  into  the  mouth  of  the  cut;  then,  veering  round 
again,  she  pushes  it  by  means  of  her  snout  to  the  end  of  the  passage, 
and  afterwards  cuts  the  crescent  in  front  of  the  hole  so  as  to  undermine 
the  egg  and  leave  it  in  a  sort  of  flap." 

5.  "Alighting  on  the  j'oung  fruit,  she  stings  or  punctures  with  her 
pincer-like  jaws  the  tender,  immature  fruit,  forces  her  snout  under  the 
skin,  puncturing  and  moving  it  about  until,  with  its  aid,  a  sufficiently 
deep  and  smooth  cavity  has  been  formed  for  the  reception  of  her  egg. 
*     *     *     *    After  oviposition,  turning  about,  with  the  aid  of  her  snout, 
the  egg  is  pushed  to  the  bottom  of  the  hole  made  for  its  reception.     This 
important  task  performed,  she  makes  with  her  mandibles  a  slight  incision 
on  one  side  of  the  cavity  where  the  egg  now  lies,  and  the  piece  thus 
formed,  is  shoved  forward,  completely  covering  the  egg,  affording  it 
protection  from  the  hot  sun,  and  hiding  it  from  the  preying  eye  of  procto- 
tupid  and  other  parasites." 

6.  "As  soon  as  the  plums,  peaches,  cherries,  and  apples  are  set, 
the  curculio  commences  operations,  imprinting  the  familiar  crescent  and 
placing  an  egg  inside." 

7.  "When  the  young  plums  are  set,  the  female  makes  the  well- 
known   crescent-shaped  cut  and  deposits   an  egg  in  the  cavity  eaten 
out." 

16.  "She   makes   a   crescent-shaped   cut   and   then   separates   and 
elevates  a  small  flap,  into  which  the  egg  is  inserted." 

17.  "When  the  young  fruits  are  formed  they  are  visited  by  the 


500  BULLETIN    No.  98.  [February, 

female,  who  cuts  a  crescent-shaped  flap  in  the  skin  and  deposits  an  egg 
under  the  flap." 

Observations  on  oviposition  were  attempted  many  times,  but  the 
records  preserved  are  for  the  most  part  fragmentary;  that  is,  they  do 
not  cover  the  whole  operation,  from  the  first  puncturing  of  the  skin 
to  the  departure  of  the  insect  from  a  completed  work. 

Observations  of  this  character  must  be  made  under  a  lens  and  it  is 
extremely  difficult  to  bring  the  lens  to  focus  and  then  maintain  the 
position  for  from  fifteen  to  twenty  minutes  without  disturbing  the  insect. 
Usually,  when  preparing  to  oviposit,  or  engaged  in  any  of  the  details 
of  the  process,  the  females  are  very  sensitive  to  jar  or  motion  of  any  kind, 
and  will  cease  work  and  change  position  on  very  slight  provocation; 
but  occasionally  they  are  so  intent  upon  the  work  that  nothing  disturbs 
them  or  causes  them  to  stop  until  the  last  detail  is  completed. 

On  several  occasions  the  process,  from  deposition  of  the  egg  to  the 
final  details  of  egg  protection,  has  been  watched;  other  records  cover 
in  some  cases  the  preparation  of  the  cavity,  in  some  the  act  of  oviposit- 
ing, in  still  others  the  final  acts  only.  In  only  three  cases  have  our 
observations  been  complete,  covering  every  detail  from  beginning  to  end. 

In  the  first  observation,  the  female  moved  about  the  apple  for  several 
seconds,  keeping  the  end  of  her  beak  in  contact  with  the  surface,  as  if 
seeking  a  favorable  spot.  When  the  exact  spot  was  decided  upon,  the 
minute  jaws  at  the  end  of  the  snout  began  a  rapid  movement  which 
quickly  made  an  opening  through  the  skin.  This  opening  was  no  larger 
than  necessary  for  admission  of  the  tip  of  the  beak.  No  skin  was  removed ; 
it  was  simply  torn  and  thrust  aside  to  give  access  to  the  pulp  below. 
Later,  as  the  excavation  proceeded,  the  broken  skin  was  seen  as  a  sort 
of  fringe  around  the  beak  at  the  surface  of  the  fruit.  As  soon  as  exca- 
vation in  the  pulp  was  commenced,  the  beak  was  deflected  backward  so 
that  the  work  was  carried  on  under  the  insect,  just  beneath  the  skin  and 
nearly  parallel  with  the  surface.  As  the  work  advanced,  the  opening 
through  the  skin  became  slightly  enlarged  by  lateral  motions  of  the  beak. 
The  pulp  was  all  eaten  as  excavated.  During  the  process  the  beak  was 
not  once  withdrawn,  nor  was  there  any  cessation  of  motion.  When  the 
excavation  of  the  cavity  was  completed  the  beak  was  withdrawn  by  a 
quick  motion,  the  insect  turned  about,  adjusted  the  tip  of  the  abdomen 
to  the  opening  and  deposited  an  egg,  which  was  forced  to  the  extremity 
of  the  excavation  by  the  ovipositor.  The  insect  now  rested  without 
motion  for  two  minutes;  then,  turning  again,  proceeded  to  cut  the  crescent 
in  front  of  the  egg.  This  crescent  puncture  was  not  wholly  a  separate 
puncture,  but,  starting  in  the  original  opening  through  the  skin,  was 
cut  laterally  in  either  direction,  partly  by  the  jaws  and  partly  by  crowd- 
ing the  beak,  first  one  way  and  then  the  other.  The  direction  of  the  beak 
was  but  little  deflected  from  the  perpendicular  and  the  cut  was  made 


1905.]  THE   CURCULIO   AND  THE  APPLK.  501 

as  deep  _as  the  length  of  the  beak  would  allow.  The  pulp  torn  away  in 
making  the  crescent  was  eaten,  just  as  was  done  in  excavating  the  egg 
cavity.  The  crescent  completed,  the  insect  walked  away,  drew  the  legs 
closely  under  the  body  and  settled  down,  apparently  to  sleep.  The 
time  occupied  in  the  process  described  was  distributed  as  follows: 

Excavating  egg  cavity 9      minutes. 

Deposition  of  egg 1      minute. 

Rest 2      minutes. 

Cutting  the  crescent 3^  minutes. 


Total 15^  minutes. 

The  egg  cavity  was  cylindrical,  with  a  rounded  bottom,  and  by 
measurement  was  found  to  be  .04  inch  in  depth.  The  egg  when  depos- 
ited very  nearly  filled  the  cavity. 

The  second  observation  of  the  complete  process  was  nearly  identical 
with  the  one  described.  The  insect  spent  no  time  in  choosing  the  exact 
spot,  but  went  to  work  at  once.  It  worked  in  a  more  leisurely  way  and 
did  not  excavate  as  deep  an  egg-cavity.  Eleven  minutes  were  spent 
on  the  cavity,  two  in  depositing  the  egg,  two  minutes  in  rest,  and  four 
minutes  in  cutting  the  crescent,  a  total  of  nineteen  minutes.  The  egg- 
cavity  measured  .035  inch  in  depth  and  was  completely  filled  by  the 
egg.  On  completion  of  the  process  the  insect  moved  a  short  distance 
and  immediately  began  a  second  cavity. 

Essential  differences  from  procedure  in  the  two  preceding  cases  were 
noted  in  the  third  complete  observation.  Excavation  of  the  egg-cavity 
was  the  same,  except  that  it  was  deeper  in  the  pulp  and  of  greater  depth. 
After  depositing  the  egg,  the  beetle  turned  and  with  her  beak  worked 
the  egg  back  to  the  bottom  of  the  cavity.  Then  she  began  tearing  off 
bits  of  skin  and  pulp,  which  were  carefully  packed  in,  above  the  egg, 
until  the  cavity  was  full.  Following  this,  the  crescent  was  cut  in  much 
the  same  manner  as  in  the  preceding  cases.  Then  she  appeared  to  make 
a  final  inspection,  and  added  some  further  packing  above  the  egg.  Finally 
the  work  appeared  to  be  satisfactory  and  she  walked  away  and  began 
a  second  puncture.  The  time  consumed  in  this  process  was  longer  than 
in  the  others,  and  was  divided  as  follows: 

Excavating  egg  cavity 12      minutes. 

Depositing  egg , \}/2  minutes. 

Placing  the  egg  with  the  beak  2      minutes. 

Packing  the  cavity : 4      minutes. 

Cutting  the  crescent 4      minutes. 

Finishing  touches 3      minutes. 

Total 26^  minutes, 


502  BULLETIN    No.  98.  [February, 

Among  the  many  cases  where  only  part  of  the  process  was  observed 
some  anomalies  were  noted.  In  two  cases  the  insect  walked  away 
immediately  after  depositing  the  egg  and  made  no  crescent  cut.  In 
three  cases,  beetles  were  seen  to  cut  crescents  and,  moving  a  short  dis- 
tance, begin  other  punctures.  These  crescents  had  no  egg  cavities  and 
no  eggs  were  deposited  in  them.  In  two  cases,  eggs  were  found  depos- 
ited directly  in  crescent  cuts,  neither  of  which  had  the  usual  egg  cavity. 
Marked  variation  in  depth  of  the  egg  cavity  was  frequently  observed. 
Not  infrequently  the  cavity  is  so  shallow  that  the  tip  of  the  egg  pro- 
trudes, and  sometimes  its  depth  is  nearly  equal  to  twice  the  length  of  the 
egg.  Packing  the  egg-cavity  with  pieces  of  pulp  is  a  common,  but  not 
universal  practice;  often  this  is  neglected,  even  where  the  cavity  is  deep. 
A  section  through  a  packed  cavity  is  shown  in  Fig.  5,  Plate  8.  Section 
of  a  deeper  cavity,  not  packed  and  somewhat  diagramatic,  may  be  seen 
at  (6)  Fig.  2,  Plate  7.  External  appearance  of  crescent  punctures  is 
shown  in  Figs.  6  and  7,  Plate  8,  and  at  (e)  and  (c)  Fig.  1,  Plate  7. 

When  reading  of  the  various  processes  and  acts  in  insect  economy, 
as  observed  and  recorded  in  published  life  histories,  it  is  quite  natural 
to  suppose  that  these  processes  are  fixed,  absolute,  and  unchangeable; 
while,  as  matter  of  fact,  many  of  them  are  subject  to  modifications. 
Sometimes  these  variations  have  apparent  reason  in  surrounding  condi- 
tions, and  again  they  can  only  be  ascribed  to  individual  peculiarity. 
The  acts  and  habits  of  an  insect  as  observed  upon  one  food  plant  may 
not  entirely  accord  with  those  of  the  same  insect  when  on  another  food 
plant.  They  vary  under  different  climates  and  under  different  seasonal 
conditions.  It  seems  entirely  possible  that,  in  the  course  of  generations, 
new  or  modified  habits  may  appear  as  apparently  fixed  characters  that 
differ  from  those  observed  when  the  life  history  was  first  recorded.  So 
it  seems  reasonable  and  practical  to  regard  modifications  from  accepted 
and  understood  procedure  as  appearing  in  the  natural  course  of  things, 
rather  than  to  look  upon  them  as  strange  or  abnormal. 

A  crescent  puncture  is  usually  supposed  to  represent  an  egg  or  an 
attempt  at  egg  laying,  but  this  does  not  always  hold  true  because,  as 
stated  above,  some  crescent  cuts  are  made  without  the  accompaniment 
of  egg  laying.  On  May  27,  1903,  fallen  apples,  twenty-five  in  number, 
were  picked  up  at  random  for  examination  of  the  crescent  punctures. 
Nearly  all  were  more  or  less  punctured  by  the  apple  curculio,  but  these 
punctures  are  not  here  considered.  Two  fruits  bore  apple  curculio 
punctures  only,  so  that  the  number  examined  for  crescent  marks  was 
twenty-three.  On  these  twenty-three  apples  were  fifty-eight  crescent 
marks,  or  2.52,  to  each  apple.  There  were  also  thirty-five  feeding 
punctures  made  by  the  plum  curculio.  Of  the  fifty-eight  crescent  cuts, 
fourteen,  or  24.14  percent,  had  no  egg-cavities  and  contained  no  eggs. 
The  remaining  forty-four  crescent  cuts  had  forty-five  egg-cavities.  Some 


\ 


6  PLATE   8 

1  Fruit  of  Crateegus,  showing  one  egg  puncture  (above)  and  one  feeding  puncture  (below). 

Made  by  apple  curculio.     Natural  size. 

2  Portion  of  surface  of  same  fruit,  showing  external  appearance  of  punctures  enlarged. 

3  Longitudinal  section  through  the  egg  puncture,  showing  egg,  enlarged. 

4  Longitudinal  section  of  the  feeding  puncture  enlarged. 

5  Section  of  egg  cavity  and  crescent  of  plum  curculio,  showing  egg  packed  in,  on  apple. 

Somewhat  enlarged. 

6  Crescent  of  plum  curculio,  showing  external  appearance,  enlarged. 

7  Crescent  of  plum  curculio,  showing  external  appearance,  enlarged. 


1905.] 


THE  CUROULIO  AND  THE  APPLE. 


503 


PLATE  7.     FIG.  1 — EXTERNAL  APPEARANCE  OF  CRESCENT  CUT. 
FIG.  2 — SECTION  OF  CRESCENT  CUT. 


504  BULLETIN    No.  98.  [February, 

variation  in  the  location  of  the  egg-cavities  was  observed;  usually  they 
occupied  the  center  of  the  crescent,  but  some  of  these  were  not  so  situ- 
ated. Of  the  forty-five  egg-cavities,  thirty-four,  or  75.56  percent,  were 
located  at  or  near  the  center  of  the  crescent;  eleven,  or  24.44  percent,  were 
located  near  the  ends  of  the  crescents.  In  one  case  there  were  two  egg- 
cavities  within  one  crescent,  one  on  each  side  half  way  between  the  center 
and  tip.  By  another  modification  one  of  the  egg-cavities,  instead  of 
being  excavated  from  the  surface,  was  excavated  from  the  bottom  at  the 
center  of  a  crescent  cut.  It  was  of  usual  dimensions,  extended  back 
obliquely  towards  the  surface,  and  contained  an  egg.  Evidently  in  this 
case  the  crescent  was  cut  first  and  the  cavity  excavated  afterwards. 

Newly  made  egg-cavities,  even  with  crescent  attachment,  are  quite 
inconspicuous  and  would  escape  notice  on  casual  examination;  but 
within  a  few  hours,  evaporation  causes  that  part  of  the  pulp  containing 
the  egg-cavity  to  shrink  and  turn  outward;  at  the  same  time  it  becomes 
discolored  and  is  then  readily  seen. 

As  the  egg-cavity  shrinks  back,  it  often  brings  the  egg  into  a  per- 
pendicular position  and  not  infrequently  the  end  of  the  egg  is  fully  exposed 
to  view.  Twenty-one  of  our  forty-five  egg-cavities  contained  eggs; 
twelve  had  contained  eggs,  but  the  eggs  had  hatched  as  was  indicated  by 
the  larval  burrows.  Twelve  were  empty  and  there  was  no  way  of  ascer- 
taining whether  eggs  had  been  laid  in  them  or  not. 

The  statements  we  have  quoted  regarding  the  details  of  oviposition 
of  the  plum  curculio,  together  with  the  observations  recorded,  indicate 
variation  in  details  sufficient  to  confuse  the  layman,  and  even  to  puzzle 
the  expert,  if  he  seek  to  cover  rightly  any  detail  with  a  general  statement 
that  will  fit  all  cases.  Two  conclusions  are  open;  either  some  individual 
insects  have  faulty  instincts,  or  there  is  more  than  one  acceptable  way  of 
performing  several  of  the  details  of  oviposition.  The  writer  accepts  the 
latter  conclusion. 

PERIOD  OF  OVIPOSITION  AND  NUMBER  OF  EGGS. 

The  length  of  the  period  during  which  oviposition  continues,  and  the 
number  of  eggs  laid  by  each  female  are  matters  of  some  importance. 
Riley  believed  "That  the  stock  of  eggs  of  the  female  consists  of  from 
fifty  to  one  hundred;  that  she  deposits  from  five  to  ten  a  day,  her  activity 
varying  with  the  temperature,"  also  "That  the  period  of  egg  depositing 
thus  extends  over  more  than  two  months."*  This  estimate  has  often 
been  quoted  and  has  been  generally  accepted. 

In  1901,  Professor  A.  L.  Quaintance  and  Mr.  R.  I.  Smith  of  Maryland 
obtained  very  interesting  records  regarding  number  of  eggs  and  length 
of  period  of  oviposition. f  Ten  females,  taken  in  copula,  were  confined 

f  3  *First  Missouri  Report,  1869,  page  54. 

tDivision  of  Entomology,  U.  S.  Dept.  Agr.  Bui.  37,  June,  1902. 


1905. 


THE   CURCULIO   AND  THE   APPLE. 


505 


separately  in  four-ounce  bottles,  supplied  each  day  with  fresh  plums, 
and  record  made  of  eggs  laid.  One  of  the  beetles  proved  to  be  a  male, 
and  one  escaped  after  seventeen  days,  so  that  the  final  complete  record 
is  for  eight  individuals  running  from  May  14th  to  the  death  of  each 
beetle.  The  record  is  as  follows: 


No. 

Date  of 
death. 

No.  of  days 
li  ing.  ' 

No.  of  days 
on  which 
eggs  were  laid. 

Total  No. 
of  eggs. 

Range  of 
eggs  laid 
per  day. 

1 
2 
4 
5 
6 
7 
9 
10 

Aug.     2 
June   20 
June   19 
Aug.     2 
July    10 
May    28 
July    31 
July    26 

81 
38 
37 
81 
58 
15 
79 
74 

70 
32 
36 
74 
37 
10 
64 
57 

276 
235 
294 
436 
270 
62 
396 
348 

1  to  15 
1  to  15 
2  to  17 
1  to  18 
2  to  15 
2  to  12 
1  to  19 
1  to  15 

This  gives  a  maximum  period  of  oviposition  of  eighty-one  days  which 
holds  for  two  of  the  beetles.  The  average  for  the  eight  beetles  is 
nearly  fifty-eight  days.  Of  the  two  living  longest,  No.  1  laid  on  seventy 
days  a  total  of  276  eggs,  an  average  of  3.94  per  day;  while  No.  5  laid  on 
seventy-four  days  a  total  of  436,  an  average  of  5.89  per  day.  No.  4  lived 
thirty-seven  days,  laid  on  thirty-six  days  a  total  of  294  eggs,  or  at  the 
rate  of  8.16  eggs  for  every  working  day.  The  number  of  eggs  laid  each 
day  by  each  beetle  ranges  from  one  to  nineteen  in  the  case  of  No.  9;  one 
to  eighteen,  for  No.  5;  two  to  seventeen,  for  No.  4;  one  to  twelve  and 
fifteen  for  the  others.  The  maximum  was  reached  about  the  last  of  May, 
after  which  the  number  per  day  diminished  rapidly.  This  record  is  an 
excellent  exposition  of  the  egg  laying  capacity  of  this  insect,  and  shows 
clearly  that  oviposition  extends  over  a  long  period. 

During  the  season  of  1903,  very  little  information  was  obtained  that 
bore  directly  upon  these  questions  of  egg  laying  capacity  and  length 
of  egg  laying  period.  The  first  eggs  were  found  on  May  12th,  two  days 
after  the  discovery  of  beetles  upon  the  trees;  the  last  egg  of  which  we 
have  record  was  deposited  on  July  12th.  The  time  difference  is  here 
sixty-one  days,  but  various  observations,  notably  the  finding  of  young 
larva?  in  September,  clearly  indicated  that  the  period  was  much  longer. 
In  the  spring  1904,  provision  was  made  for  testing  the  egg  laying  capacity 
and  for  ascertaining  the  length  of  the  egg  laying  period.  The  appearance 
of  the  beetles  was  so  tardy  that  enough  for  our  purpose  were  not  secured 
until  May  23d.  On  that  date,  nineteen  pairs  were  obtained,  all  taken 
in  the  act  of  mating.  Each  pair  was  placed  in  a  jelly  glass;  the  glasses 
were  numbered,  supplied  with  apples,  and  covered  with  squares  of  cheese- 
cloth held  in  place  by  rubber  bands.  Three  days  later,  on  May  26th,  an 
additional  pair  was  secured,  making  twenty  in  all.  The  glasses  were 
arranged  on  a  table  in  our  laboratory,  as  shown  in  Plate  9,  and  were  not 
disturbed  except  at  regular  intervals  when  the  apples  were  changed, 


506 


BULLETIN    No.  98. 


[February, 


1905.]  THE   CURCULIO   AND  THE  APPLE.  507 

The  hours  for  change  of  fruits  were  fixed  at  6:30  in  the  morning  and  at 
8:30  in  the  evening,  and  were  closely  adhered  to  throughout  the  season. 
The  female  of  pair  No.  8  deposited  only  eight  eggs  as  follows:  two  on 
May  30th,  one  each  on  June  16th,  25th  and  27th,  two  on  July  1st,  and 
one  on  July  4th.  The  pair  was  as  active  as  others,  and  both  lived  to 
August  15th.  One  died  then  and  the  remaining  one  lived  to  September 
19th,  but  the  egg  production  is  so  far  below  all  others  that  we  discard  the 
pair  from  our  tabulation  of  results.  The  female  of  pair  No.  12  laid  two 
eggs  on  May  27th,  and  died  on  June  1st;  this  eliminated  the  pair.  Up  to 
June  18th  no  egg  had  been  laid  by  the  female  of  pair  No.  14,  and  on  that 
date  she  was  removed  and  a  new  one  substituted.  This  new  one  laid  two 
eggs  the  day  she  was  placed  in  the  glass,  but  none  after  that  day,  although 
she  lived  until  August  10th.  The  male  did  not  die  until  September  10th. 
These  two  pairs,  No.  12  and  No.  14,  are  also  excluded  from  our  tabulated 
record,  so  that  we  have  remaining  butseventeen  pairs.  The  record  of  two 
of  these  is  incomplete.  No.  5  escaped  on  June  16th  and  No.  11  on  June 
26th.  All  others  are  recorded  for  the  duration  of  life. 

The  tabulation  on  page  508  brings  into  compact  form  the  details  re- 
corded for  each  pair. 

The  apples  as  removed  were  carefully  examined  under  a  lens  and 
record  made  of  eggs  and  punctures  found.  Use  of  the  knife  was  genera- 
ally  necessary  to  determine  the  presence  of  eggs,  because  external  ap- 
pearances cannot  be  depended  upon,  and  no  egg  was  recorded  until  seen. 
The  number  of  eggs  without  crescents  and  the  number  of  crescents  with- 
out eggs  are  recorded,  as  showing  the  frequency  of  departure  from  what 
is  generally  regarded  as  normal  procedure.  Thus  No.  18  made  a  total  of 
311  crescents,  sixty-five  of  which  were  unaccompanied  by  egg-laying; 
she  also  laid  three  eggs  that  had  no  accompanying  crescent.  No.  2  made 
263  crescents,  forty  of  which  were  not  accompanied  by  eggs  and  twelve 
out  of  her  235  eggs  had  no  crescents  appended.  The  total  number  of 
crescents  made  by  the  seventeen  females  is  2,206  and  of  these  307,  or 
13.92%,  were  unaccompanied  by  eggs.  On  the  other  hand,  fifty-four 
eggs  were  found  unaccompanied  by  the  usual  crescent;  this  is  2.76%  of  the 
1,954  eggs  laid. 

Wide  differences  in  the  egg  laying  capacity  of  individuals  appear. 
Thus  our  maximum  number  of  eggs,  263,  was  laid  by  No.  10  on  sixty- 
nine  of  the  one  hundred  days  in  confinement,  while  No.  16  laid  only 
thirty-four  eggs  on  twenty-five  out  of  her  102  days  under  observation, 
and  No.  20  in  her  eighty-seven  days,  oviposited  on  only  eleven  days,  and 
has  a  total  of  only  fourteen  eggs. 

The  time  between  deposition  of  the  first  egg,  May  25th,  and  deposition 
of  the  last  egg  September  9th,  or  107  days,  may  be  taken  as  the  duration 
of  the  egg  laying  period,  but  there  is  great  variation  in  individuals  and 
this  full  period  was  reached  by  none.  The  nearest  approach  is  by  No.  17. 


508 


BULLETIN    No.  98. 


[February, 


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1905.]  THE  CURCULIO   AND  THE  APPLE.  509 

This  insect  deposited  the  first  egg  May  27th  and  the  last  September  9th, 
a  period  of  105  days.  The  next  longest  period  between  first  and  last  days 
is  for  No.  2,  May  26th  to  September  3d,  or  ninety-nine  days;  then  follows 
No.  13  with  ninety-seven  days,  No.  16  with  eighty-one  days,  and  No.  10 
with  seventy-five  days.  Leaving  out  the  two  incomplete  records,  No.  7 
has  the  shortest  period,  twenty-eight  days,  but  this  is  within  four  days 
of  her  total  time.  No.  9  has  a  period  between  first  and  last  eggs  of  only 
thirty-five  days.  Her  last  egg  was  deposited  July  1st,  and  she  lived  until 
July  26th.  Including  all  of  the  seventeen  insects  under  observation, 
the  average  time  between  first  and  last  egg  is  57.88  days  while  the  average 
time  under  observation  is  80.64  days.  Several  of  the  insects  lived  for 
from  ten  to  twenty  days  after  their  last  eggs  were  deposited,  and  those 
having  long  periods  attain  this  record  because  intervals  of  three  to  seven 
days  between  eggs  were  common  after  about  the  first  of  August. 

Fresh  fruits  were  supplied  twice  each  day  in  order  to  ascertain  the 
distribution  of  the  work  over  day  and  night.  Did  oviposition  continue 
at  night,  and  if  so  to  what  extent?  Results  indicate  a  nearly  even  dis- 
tribution, although  the  twenty-four  hours  were  not  divided  equally. 
The  number  laid  in  the  daytime  is  1,037  as  against  917  laid  at  night. 
As  the  season  advanced  and  the  days  lengthened  there  would  be  a  period 
of  daylight  before  examination  in  the  morning,  and  to  insure  darkness 
between  the  examination  at  night  and  the  next  morning  the  glasses  were 
placed  upon  a  cloth  mat  and  covered  with  tin  cans  so  that  the  insects 
were  in  absolute  darkness  during  the  night  period.  This  practice  was 
continued  for  several  weeks,  but  as  it  apparently  made  no  difference  was 
finally  discontinued.  The  greater  number  of  feeding  punctures  were 
made  at  night.  Of  the  5,631  feeding  punctures  recorded,  2,594  were 
made  during  the  day  period  and  3,037  during  the  night,  an  excess  of  443 
in  favor  of  night  as  a  time  for  feeding. 

Comparing  our  record  of  eggs  laid,  with  the  results  obtained  by  Pro- 
fessor Quaintance,  wide  differences  appear.  His  eight  females  produced  a 
total  of  2,317  eggs,  while  our  seventeen  gave  only  1,954.  The  average 
in  one  case  is  289.62,  in  the  other  114.94.  His  most  prolific  insect  laid 
436  eggs,  ours  produced  but  263.  The  differences  in  number  of  eggs 
laid  may  in  part  account  for  the  differences  in  length  of  life.  In  the 
Maryland  experiment  the  last  insect  died  on  August  2d  after  eighty-one 
days  confinement.  Our  No.  6  died  on  September  26th  after  127  days 
in  confinement. 

It  is  possible  that  the  plums  supplied  in  Maryland  were  more  accept- 
able to  the  insects  than  were  the  apples  furnished  the  insects  in  Illinois, 
but  we  are  inclined  to  regard  differences  in  climate  as  the  more  probable 
cause  of  the  differences  in  number  of  eggs  and  period  of  oviposition  shown 
by  the  two  records.  High  temperatures  and  great  humidity  are  factors 
tending  to  accelerate  egg  production.  It  was  frequently  observed  during 


510 


BULLETIN    No.  98. 


[February, 


the  summer  that  oviposition  was  most  rapid  on  warm  days  and  that  very 
few  eggs  were  laid  during  periods  when  the  temperatures  ran  low.  The 
summer  throughout  was  cool,  there  were  few  warm  days,  and  none  of  the 
excessively  hot  days  that  characterized  the  summer  of  1903. 

It  is  presumable  that  Maryland  temperatures  were  relatively  higher, 
and  that  the  prevailing  humidity  was  greater  than  in  Illinois.     In  the 
absence  of  definite  data  it  is  only  possible  to  suggest  probable  causes  of 
difference,  but  whatever  the  causes  may  have  been,  the  records  show 
the  fact  of  wide  differences  in  the  two  sets  of  insects. 


NUMBER  OF  PUNCTURES  FOUND  ON  FALLEN  APPLES. 

At  intervals  during  the  summer  of  1903,  fallen  fruit  was  gathered, 
critically  examined,  and  record  made  of  the  number  and  purpose  of  the 
punctures,  and  number  of  eggs  and  larvae.  The  results  of  this  exami- 
nation are  tabulated  below  as  an  illustration  of  the  extent  of  the  work 
done  by  the  plum  curculio: 


Date. 

No.  of 
apples. 

Total 
punc- 
tures. 

Crescent 
punc- 
tures. 

Feeding 
punc- 
tures. 

Eggs. 

Larvae. 

Living. 

Dead. 

May  14-18 
June  17-18 
July  10-30 

405 

285 
26 

753 
969 
517 

286 
649 
102 

467 
320 
415 

144 
5 
9 

31 
32 
3 

32 
64 

7 

Totals  

716 

2239 

1037 

1202 

158 

66 

103 

Every  apple  here  examined  had  been  visited  by  the  plum  curculio, 
and  the  total  of  716  apples  bore  2,239  punctures.  The  average  for  the 
apples  examined  in  May  is  1.86  punctures  to  each  fruit;  for  apples  exam- 
ined in  June,  3.40  punctures  to  each  fruit;  and  for  the  few  examined  in 
July,  19.88  punctures  to  each  fruit.  A  little  more  than  half  the  total 
number  of  punctures,  or  1,202,  were  distinctively  for  feeding.  On  the 
apples  examined  in  May  and  June  these  feeding  punctures  were  small, 
cylindrical  excavations  extending  straight  into  the  fruit  at  right  angles 
to  the  surface,  and  were  seldom  enlarged  below.  Feeding  punctures  on 
the  apples  examined  in  July  were  for  the  most  part  enlarged  below, 
so  that  the  excavation  in  the  pulp  was  from  three  to  four  times  the 
diameter  of  the  surface  opening. 

The  crescent  punctures  numbered  1,037,  or,  given  in  percentages, 
46.32%  of  the  punctures  were  crescents,  and  53.68%  feeding  punctures. 
Division  of  punctures  by  percentages  for  the  different  months  would  be 
as  follows: 

May,  37 . 98%  crescents  and  62 . 02%  feeding  punctures. 
June,  66.97%  crescents  and  33.13%  feeding  punctures. 
July,  19 . 73%  crescents  and  80 . 27%  feeding  punctures. 


1905.]  THE  CURCULIO    AND  THE  APPLE.  511 

These  figures  simply  help  to  illustrate  what  has  been  generally  ob- 
served, that  crescent  punctures  multiply  most  rapidly  during  June,  and 
that,  as  the  season  advances,  feeding  punctures  become  proportionately 
more  numerous. 

Our  tabulation  above  records  158  eggs  and  169  larvae,  a  total  of  327. 
Associate  each  one  of  these  with  a  crescent  mark  and  we  still  have  710 
crescents  which  must  be  accounted  unproductive.  These  would  include 
crescents  made  without  the  accompaniment  of  egg  laying,  those  whose 
accompanying  eggs  had  been  destroyed,  and  those  whose  eggs  had 
hatched,  the  larvae  having  developed  and  left  the  fruit.  An  effort  was 
made  to  separate  these  classes,  but  so  many  uncertainties  were  encoun- 
tered that  the  attempt  was  abandoned.  However,  it  may  be  stated 
with  certainty  that  the  number  of  crescents  cannot  be  taken  as  an  index 
of  the  egg  laying  capacity  of  the  insect.  August  5,  1904,  seventy- three 
apples  were  collected  in  an  unsprayed  orchard  near  Griggsville  and 
examined  for  curculio  punctures.  Seventy  of  these  apples  bore  393 
crescent  punctures,  and  on  63  of  the  lot  422  feeding  punctures  made  by 
the  plum  curculio  were  found.  Apple  curculio  injury  was  much  less 
common.  Twenty-one  of  the  apples  bore  27  egg  punctures,  and  29 
carried  112  feeding  punctures. 

August  24,  471  apples  were  picked  from  trees  in  another  orchard 
that  had  not  been  sprayed  and  in  which  the 'conditions  for  insect  develop- 
ment were  very  favorable.  One  of  these  apples  was  free  from  puncture. 
On  417  of  these  apples  1,762  crescent  punctures  were  counted.  This  is 
4.22  punctures  for  each  apple  punctured.  The  feeding  punctures  made 
by  plum  curculio  numbered  4,264,  and  were  distributed  on  457  apples, 
or  at  the  rate  of  9.33  punctures  for  each  apple. 

The  apple  curculio  injury  was  unusually  small;  seven  apples  bore 
eight  egg  punctures  and  31  apples  bore  47  feeding  punctures.  In  gather- 
ing these  apples  they  were  taken  at  random  as  they  came  to  hand,  and 
the  lot  fairly  represents  the  whole  orchard,  which  is  about  ten  acres  in 
area. 

The  following  figures  bearing  upon  the  extent  to  which  apples  are 
punctured  and  the  proportion  of  crescent  marks  as  compared  with 
feeding  punctures  are  given  by  Mr.  E.  S.  G.  Titus,  then  assistant  to  the 
State  Entomologist,  and  were  obtained  from  an  examination  of  apples 
on  the  trees  at  three  different  places  in  southern  Illinois  in  the  spring 
of  1902.*  In  one  lot  of  104  apples,  27,  or  25.96%,  were  marked  by 
58  punctures,  12,  or  20.69%,  of  which  were  crescents.  In  a  second  lot 
of  100  apples,  68  were  marked  by  249  punctures,  one-third  of  which 
were  crescents.  Of  the  third  lot  of  50  apples,  23,  or  46%,  were  marked 
by  38  punctures,  26,  or  68.42%  of  which  were  crescents.  Further, 
regarding  plum  curculios  supplied  with  apples  in  confinement,  Mr.  Titus 

transactions  Illinois  State  Horticultural  Society,  1902,  page  158. 


512  BULLETIN    No.  98.  [February, 

says:  "Four  females  made  in  four  days  46  egg  punctures  and  161 
feeding  pits.  Eight  females  made  in  this  time  48  egg  punctures,  in  which 
were  19  eggs,  and  203  feeding  pits.  Three  males  made  63  feeding  punc- 
tures in  two  days.  Four  pairs,  males  and  females,  made  in  four  days  327 
feeding  pits,  and  the  females  of  these  pairs  made  28  egg  punctures  in 
the  same  time." 

Professor  F.  M.  Webster  reports,*  rinding  158  egg  punctures  on  136 
apples  examined,  and  from  these  apples  eight  adult  curculios  were  bred. 

The  figures  above  given  are  sufficient  to  illustrate  the  wonderful 
industry  of  the  plum  curculio.  The  work  of  making  punctures  begins 
as  soon  as  apples  begin  forming,  and  continues  as  long  as  the  fruit  remains 
upon  the  trees.  Each  puncture  means  a  blemish,  greater  or  less,  accord- 
ing to  the  purpose  of  the  puncture  and  the  season  when  made.  The  great 
majority  of  the  apples  punctured  for  egg-laying  purposes  fall  early. 
Such  as  remain  on  the  trees  are  ruined  by  the  abundant  feeding  punc- 
tures, especially  by  those  made  in  late  summer  and  fall.  Not  infrequently 
the  whole  side  of  a  fruit  will  collapse,  owing  to  running  together  of  the 
excavations  in  the  pulp.  One  such  fruit  examined  under  a  lens  showed 
61  punctures  within  the  borders  of  the  collapsed  area;  seven  of  these 
were  made  by  the  apple  curculio  and  54  by  the  plum  curculio.  This 
same  fruit  had  31  separate  and  distinct  punctures  outside  the  area  first 
examined;  nine  of  these  were  made  by  the  apple  curculio  and  22  by 
the  plum  curculio.  Here  were  92  punctures,  all  made  for  feeding  pur- 
poses, on  one  Ben  Davis  apple  that  measured  one  and  one-fourth  inches 
in  transverse  diameter.  This  apple  was  taken  from  the  tree  July  10th. 
Other  apples  selected  as  being  badly  punctured  were  examined  August 
24th,  and  gave,  54,  28,  63,  47,  and  38  punctures,  respectively.  In  1903 
apples  were  examined  in  several  orchards  in  the  neighborhood  of  Barry, 
and  these  apples  were  everywhere  found  to  be  badly  punctured.  The 
crop  was  light  and  undoubtedly  punctured  worse  than  would  have  been 
the  case  had  the  trees  borne  a  full  crop,  but  there  were  enough  apples 
to  demonstrate  the  abundance  of  the  insects  and  their  capacity  for  doing 
injurious  work. 

ADDITIONAL   NOTES  ;ON   CRESCENT   PUNCTURES. 

Differences  in  feeding  punctures  have  already  been  referred  to.  There 
are  also  differences  in  crescent  punctures,  modifications  from  the  normal 
form  which  frequently  appear  in  the  latter  part  of  the  season,  and  seem 
to  be  due  to  circumstances  rather  than  to  individual  peculiarities  or  any 
direct  influence  of  season.  Observations  on  the  crescent  cuts  made  by 
the  seventeen  females  kept  in  confinement  during  the  past  season  show 
that  the  several  forms  may,  at  different  times,  be  made  by  any  individual. 
Upon  plums,  the  crescent,  so  far  as  my  observation  goes,  is  very  uniform 
*Purdue  University  Experiment  Station  Bulletin  33,  October,  1890. 


1905.]  THE   CURCULIO    AND   THE   APPLE.  513 

in  shape,  appearing  usually  as  in  Fig.  4,  Plate  2;  only  slight  variations 
have  been  seen;  but  on  the  apple  the  modification  from  the  usual  cres- 
centic  form  is  often  considerable.  So  far  as  external  appearance  is  con- 
cerned, this  modification  commonly  consists  in  a  shortening  of  the  horns 
of  the  crescent,  often  to  such  an  extent  that  the  cut  appears  perfectly 
straight;  or  the  cut  may  be  reduced  to  an  irregular  form  or  be  perfectly 
circular.  But  whatever  the  external  appearance,  if  the  cut  was  designed 
to  serve  the  purpose  of  a  crescent  cut,  it  goes  deep  and  extends  back 
underneath  the  egg-cavity.  This  cut  backward  is  also  true  of  those  per- 
fectly made,  but  apparently  purposeless  crescents  referred  to  as  unaccom- 
panied by  egg-cavities  or  eggs.  If  an  egg  deposited  in  a  normal  cavity 
accompanied  by  the  crescent  cut  fails  to  hatch,  or  if  the  larva  dies  soon 
after  hatching,  development  of  the  apple  usually  continues.  In  these 
cases  the  crescent  puncture  frequently  grows  out  in  such  manner  that  it 
finally  leaves  only  a  more  or  less  irregularly  shaped  russet-colored  spot 
upon  the  surface  of  the  apple1.  Such  a  spot  is  illustrated  by  Fig.  3,  Plate 
18.  This  mark  cannot  be  regarded  as  a  serious  blemish. 

From  observation  of  the  beetles  at  work,  the  conclusion  is  formed  that 
modifications  from  the  normal  crescentic  form  are  not  due  to  faulty  in- 
stinct, or  lack  of  care  on  the  part  of  the  insect,  but  to  circumstances  under 
which  the  work  is  done.  In  making  punctures,  the  force  necessary  to 
press  the  jaws  at  the  end  of  the  beak  into  the  skin  or  pulp  is  mainly 
derived  from  the  pull  by  the  legs,  and  this  can  not  be  exerted  unless  the 
feet  are  securely  anchored.  On  several  occasions  beetles  have  been  seen 
to  waive  the  attempt  to  make  punctures  because  of  inability  to  anchor 
the  feet.  Young  apples,  still  covered  with  thick  pubescence,  afford  secure 
anchorage  at  any  point,  and  here  the  crescents  are  found  to  be  quite  uni- 
form in  shape.  Later  in  the  season,  as  the  apples  enlarge,  the  surface 
presents  less  curvature,  and,  unless  marked  by  some  defect,  becomes 
perfectly  smooth,  and  the  beetle,  unable  to  gain  secure  footing,  has  diffi- 
culty in  making  any  puncture  at  all,  and  often  leaves  the  work  incomplete 
or  of  altered  form.  If  the  apple  is  slightly  wilted  or  has  a  slightly  rough- 
ened surface,  beetles  have  no  trouble  in  anchoring  the  feet  securely,  and 
under  these  circumstances  punctures  of  normal  size  and  form  are  made. 
Very  old  beetles,  even  though  securely  anchored,  are  often  unable,  either 
from  weakness  due  to  old  age  or  from  injury  to  the  jaws,  to  make  a  punc- 
ture at  all,  and  no  doubt  many  die  from  starvation  because  of  inability  to 
puncture  the  skin  and  gain  access  to  the  edible  fruit  pulp. 


514  BULLETIN    No.  98.  [February, 

THE  APPLE  CURCULIO. 

The  apple  curculio  has  been  known  as  injurious  for  a  much  shorter 
period  than  has  the  plum  curculio,  and  it  has  never  been  so  serious  a 
menace  to  fruit  crops,  never  has  developed  the  interest  or  received  the 
attention  that  has  been  accorded  the  plum  curculio.  It  follows  that  the 
published  accounts  of  the  apple  curculio  are  as  meager  as  the  accounts  of 


PLATE  10.    THE   APPLE  CURCULIO,  ENLARGED. 

the  plum  curculio  are  voluminous.  There  is  very  little  of  historical  mat- 
ter regarding  the  insect. 

The  apple  curculio,  Anthonomus  guadrigibbus,  was  named  and  de- 
scribed by  Say,  in  1831.  He  gives  the  habitat  as  the  United  States,  and 
the  food  plant  upon  which  it  breeds  as  Crataegus.  The  earliest  record 
which  we  have  been  able  to  find  indicating  injury  to  the  apple  by  this 
nsect  is  that  by  B.  D.  Walsh  in  the  Prairie  Farmer  for  August  27,1864, 
and  this  account  appears  to  have  been  first  published  in  the  Valley 
Farmer. 

Mr.  Walsh  here  states  that  the  insect  has  long  been  known  to  infest 
the  wild  crab,  and  ascribes  the  discovery  that  it  would  breed  in  cultivated 
apples  to  Mr.  William  Cutler,  of  Beverly,  Illinois.  Mr.  Cutler  reported 
that  the  first  punctures  were  noticed  May  26th,  and  that  June  12th  fully 
half  the  fruit  on  trees  that  promised  ten  to  fifteen  bushels  per  tree  had 
been  punctured. 

In  succeeding  years  there  are  occasional  notices  of  injury  done  by 
these  insects.  These  reports  come  mainly  from  Illinois,  Missouri,  Iowa, 
and  Wisconsin,  but  injury  is  also  reported  from  Connecticut,  New  Jersey, 
Pennsylvania,  North  Carolina,  and  other  Southern  states. 

The  native  food  plants  of  the  apple  curculio  are  the  wild  crab  and  the 
hawthorn  (Cratcegus).  Both  these  plants  are  widely  distributed;  the 


1905.]  THE   CTJRCULIO   AND  THE  APPLE.  515 

former  represented  by  about  four  species,  the  latter  by  fifteen  species. 
Whether  the  apple  curculio  breeds  in  all  species  or  not  does  not  appear  to 
be  known,  nor  is  its  geographical  range  at  all  well  defined. 

In  Pike  County  the  insect  was  found  ovipositing  in  fruits  of  the 
Western  crab-apple,  Malusicnsis,  and  of  the  scarlet  haw,  Crataegus 
coccin'u,  but  it  was  very  much  more  abundant  upon  the  haw  than  upon 
the  crab-apple. 

Dr.  Le  Baron  says,  "Records  lead  to  the  conclusion  that  this  insect  is 
rather  a  Southern  species,  more  abundant  South  than  North."  *  This  is 
probably  true  as  far  as  injuries  to  apples  are  concerned,  for  most  of  the 
reports  of  injuries  by  this  insect  made  since  Le  Baron  wrote  the  above 
come  from  southern  localities.  That  the  insect  is  distributed  well  to  the 
north  is  indicated  by  the  following  from  Saunders:  "But  in  most  of  the 
Northern  states  and  in  Canada,  although  common  on  thorn  bushes  and 
crab-apples,  it  seldom  attacks  the  more  valuable  fruits  to  any  consider- 
able extent."  f 


HABITS  AND    LIFE   HISTORY. 

The  main  facts  in  the  life  history  of  the  apple  curculio  are  well  estab- 
lished, and  were  first  clearly  set  forth  by  Riley  in  his  Third  Missouri  Report 
in  1871.  Oviposition  begins  in  the  spring,  while  the  fruits  are  quite  small. 
The  larvse  feed  on  the  pulp,  pupate  in  the  cavity  excavated,  and  emerge 
from  the  fruit  as  perfect  beetles.  This  new  generation  of  beetles  for  the 
most  part  hides  away  in  secure  places  until  late  fall,  then  hibernates  until 
time  for  ovipositing  in  the  spring. 

Very  few  definite  data  regarding  the  length  of  the  various  stages — egg, 
larva,  pupa,  and  beetle — are  to  be  found  in  the  written  accounts  of  this 
insect.  Of  the  larva  Riley  says,  "It  feeds  for  nearly  a  month,"  and  of 
the  pupa  he  says,  "After  remaining  in  this  state  from  two  to  three  weeks, 
it  undergoes  another  moult,  and  the  perfect  beetle  state  is  assumed." 
The  difficulty  in  obl&ining  exact  data  on  these  matters  is  appreciated 
when  we  consider  that  all  of  the  changes  occur  while  the  insect  is  sealed 
within  the  fruit,  and  cannot  be  examined  without  disturbing  natural 
conditions. 

During  the  two  seasons  of  1903  and  1904,  over  which  this  investigation 
of  curculios  in  relation  to  the  apple  in  Pike  County  has  extended,  the 
main  effort  was  directed  against  the  plum  curculio,  as  much  the  more  in- 
jurious of  the  two  species,  but  some  facts  regarding  the  apple  curculio 
have  been  gathered  and  may  properly  be  given  place  here. 

In  the  spring  of  1903,  search  was  made  for  the  beetles  April  15th,  and 

*Prairie  Farmer,  1873,  209. 
flnsects  Injurious  to  Fruits,  135 


516  BULLETIN    No.  98.  [February, 

at  frequent  intervals  after  that  date.  None,  however,  were  found  until 
April  27th,  and  then  only  a  single  specimen  taken  among  dead  leaves  of 
grass  in  close  contact  with  the  ground.  Search  among  rubbish  on  the 
ground  was  continued,  and  trees  were  carefully  examined,  but  no  more 
beetles  were  found  until  May  10th.  On  this  date,  two  specimens  were 
taken  from  a  Ben  Davis  tree.  The  next  day  others  were  found  and  the 
12th  beetles  were  very  common.  They  appeared  to  come  all  at  once 
in  company  with  the  plum  curculio.  May  13th  hawthorn  trees  in  wood- 
land adjoining  the  orchard  were  observed  to  be  much  infested,  and 
several  specimens  were  taken  from  fruits  of  the  wild  crab-apple.  The 
insects  were  mating,  oviposition  was  in  progress,  and  feeding  punctures 
were  multiplying  rapidly. 

In  the  spring  of  1904,  search  for  beetles  in  hibernating  quarters  was 
unsuccessful ;  none  were  found.  The  first  beetle  found  was  taken  from  an 
apple  tree  May  2d;  a  second  was  taken  May  12th.  Several  were  taken 
May  19th,  and  at  various  times  after  that  date,  but  throughout  the  season 
they  were  much  less  abundant  than  in  1903.  In  fact,  for  most  of  the  season 
the  beetles  were  rare  upon  orchard  trees.  May  19th,  beetles  were  taken 
in  considerable  numbers  from  fruits  of  hawthorn  in  adjoining  forest,  and 
for  several  weeks  the  insects  were  abundant  on  these  native  trees.  This 
was  the  source  from  which  we  drew  our  supplies  of  this  insect  for  labora- 
tory purposes. 

THE  EGG. 

The  eggs  of  the  apple  curculio  are  quite  uniform  in  size,  and  from 
measurements  of  ten  are  found  to  be  about  .04  inch  in  length  and 
.02  inch  in  transverse  diameter.  When  first  laid  they  are  of  a  pearly 
white  color.  Apparently  they  swell  somewhat  by  absorption  of  the 
juices  in  the  cavity,  and  within  a  day  or  two  after  being  deposited  assume 
a  dingy  yellowish  color. 

The  length  of  the  egg  stage  was  determined  to  the  hour  for  eight  in- 
dividuals, and  the  range  is  from  one  hundred  hours  to  one  hundred  and 
seven  hours,  with  an  average  of  one  hundred  and  ffte  hours,  or  four  days 
and  nine  hours.  Without  doubt  high  temperatures  accelerate  and  low 
temperatures  retard  the  hatching  of  eggs. 

OVIPOSITION. 

The  first  and  only  description  of  the  process  of  oviposition  of  the 
apple  curculio  that  has  been  found  is  that  recorded  by  Professor  C.  P. 
Gillette  in  Bulletin  No.  11,  of  the  Iowa  Experiment  Station,  issued  in 
November,  1890.  This  record  accords  closely  with  our  observations 
made  in  Pike  County. 

The  apple  curculio,  like  the  plum  curculio,  varies  the  form  of  the 
puncture  considerably  and  individuals  differ  greatly  in  the  time  required 


1905. 


THE   CURCULIO   AND  THE   APPLE. 


517 


to  complete  the  process.  The  position  of  this  insect  when  engaged  in 
excavating  the  egg-cavity  is  shown  in  Fig.  1,  Plate  11.  The  apple  cur- 
culio  is  much  less  shy  than  the  plum  curculio,  and  no  difficulty  was  ex- 
perienced in  bringing  under  observation  insects  engaged  in  the  act  of 
oviposition.  Twigs  bearing  fruits  upon  which  curculios  were  working 
were  removed  from  trees  and  arranged  in  positions  convenient  for  obser- 
vation without  causing  any  cessation  of  work.  Bringing  the  working 
insects  into  focus  of  the  lens  necessitated  getting  close  to  them,  but  this 
did  not  disturb  them  nor  cause  them  to  stop  work.  The  complete  opera- 
tion of  making  the  egg-cavity,  depositing  the  egg,  and  sealing  the  cavity 
was  observed  and  timed  in  ten  cases.  In  twelve  additional  cases  the 
latter  part  of  the  operation,  that  is  to  say,  the  deposition  of  the  egg  and 
the  sealing  of  the  cavity,  was  in  like  manner  observed  under  a  lens.  In 
the  ten  cases  where  the  entire  process  was  observed,  the  work  was  iden- 
tical, except  in  the  matters  of  the  time  consumed,  form  of  the  cavity, 
and  in  the  fact  that  five  of  the  beetles  rested  for  a  time  after  completing 
the  cavity  and  before  turning  to  place  the -egg.  The  time  consumed  in 
each  operation  is  given  below : 

APPLE  CURCULIO — TIME  CONSUMED  IN  OVIPOSITION. 


. 

Date  of 

>Jr» 

Excavating 

Avest  in 

Ovi- 

Seal- 

Total 

observation. 

li  O. 

cavity. 

min- 
utes. 

positing. 

ing. 

time. 

May  13,  1903 

1 

1  hr.  10  min. 

4  min. 

2  min. 

1  hr.  16  min. 

May  13,  1903 

2 

1  hr.  16  min. 

9 

5  min. 

1  min. 

1  hr.  31  min. 

Mav  13,  1903 

3 

2  hr.  20  min. 

8  min. 

2  min. 

2  hr.  30  min. 

May  14,  1903 

4 

1  hr.  40  min. 

2 

5  min. 

2  min. 

1  hr.  49  min. 

May  14,  1903 

5 

1  hr.  24  min. 

5 

4  min. 

3  min. 

1  hr.  36  min. 

May  15,  1903 

6 

1  hr.  22  min. 

4  min. 

2  min. 

Ihr.  28  min. 

June   4,  1904 

7 

40  min. 

2  min. 

1  min. 

43  min. 

June   4,  1904 

8 

1  hr.  13  min. 

1 

6  min. 

2  min. 

1  hr.  22  min. 

June   7,  1904 

9 

59  min. 

6  min. 

2  min. 

1  hr.    7  min. 

June    7,  1904 

10 

1  hr.    6  min. 

2 

5  min. 

3  min. 

1  hr.  16  min. 

The  average  time  is  about  one  hour  and  twenty-eight  minutes. 

No.  3  was  an  exceptionally  small  beetle  and  consumed  an  unusual  time 
in  the  operation.  No.  7  was  extremely  active  and  strong  and  completed 
the  process  in  less  than  half  of  the  average  time.  The  insect  begins  work 
by  tearing  the  skin  of  the  fruit  sufficiently  to  give  access  to  the  pulp. 
Little  or  no  skin  is  removed ;  the  particles  torn  generally  remain  attached 
and  as  the  beak  is  worked  into  the  fruit  appear  as  an  irregular  fringe 
about  the  point  of  entry.  For  the  first  fifteen  or  twenty  minutes,  the 
beak  is  worked  slowly  downward  with  no  lateral  motion ;  then  it  is  par- 
tially withdrawn  and  worked  downward  along  one  side  with  an  inter- 
rupted chisel-like  motion.  This  is  repeated,  and  as  the  cavity  enlarges, 
the  head  is  twisted  more  and  more  to  one  side  or  the  other.  This  motion 
slightly  enlarges  the  surface  opening.  The  depth  of  the  excavation  is 
as  great  as  the  length  of  the  beak  will  allow,  and  towards  the  end  of  the 


518 


BULLETIN    No.  98. 


[February, 


PLATE  11.     FIG.   1 — APPLE  CURCULIO  MAKING  EGG  PUNCTURE.     xSJ^. 

FIG.  2 — EXIT  HOLE  OF  APPLE  CURCULIO  IN  SMALL  APPLE,  x 
FIG.  3 — APPLE  CURCULIO  PUPA  IN  APPLE.     x3J^. 


1905.]  THE   CURCULIO   AND  THE  APPLE.  519 

work  the  head  is  pressed  into  the  opening  until  the  eyes  are  half  buried, 
the  antennae  being  pressed  back  against  the  beak  with  only  the  ultimate 
joints  protruding.  Unless  greatly  disturbed  the  beak  is  at  no  time 
wholly  withdrawn  until  the  excavation  is  complete.  The  pulp  as  exca- 
vated is  eaten  by  the  insect  and,  in  each  case  observed,  copious  excretion 
occurred  from  eight  to  twelve  times  during  the  operation.  The  excavation 
completed  to  the  satisfaction  of  the  insect  the  beak  is  withdrawn.  In 
five  cases  the  insect  turned  at  once,  applied  the  tip  of  the  abodomen  to 
the  opening  and  deposited  an  egg.  In  the  other  five  cases  the  insect 
rested  without  motion  for  from  one  to  nine  minutes  before  turning  to 
deposit  the  egg.  Almost  immediately  after  the  egg  is  dropped,  the  insect 
deposits  over  the  opening  a  mass  of  excrement  which  is  greenish  in  color 
and  of  viscid  appearance.  By  an  up-and-down  motion  of  the  tip  of  the 
abdomen  this  matter  is  crowded  into  and  plastered  down  over  the  opening, 
effectually  sealing  it,  then  the  insect  quickly  walks  away.  In  three  of  the 
ten  cases,  after  a  short  period  of  rest  the  insect  took  wing  and  flew  into  a 
near-by  tree;  two,  after  resting,  began  other  punctures;  the  others  were  still 
resting  when  the  observations  were  discontinued.  When  an  insect  leaves 
after  oviposition,  there  is  so  little  surface  evidence  of  the  work  that  it 
would  not  be  noticed,  and  can  only  be  detected  by  careful  examination. 
In  a  few  hours,  however,  the  plug  becomes  brown  and  finally  black;  in 
drying  it  hardens.  It  effectually  -seals  the  opening  and  remains  per- 
manently. Figures  1,  2,  3,  and  4,  Plate  8,  serve  to  illustrate  punctures 
of  the  apple  curculio.  Fig.  1  is  a' hawthorn  fruit  natural  size,  in  which 
are  two  punctures  appearing  as  minute  black  dots;  Fig.  2  is  a  portion  of 
the  fruit  showing  the  dots  enlarged.  The  upper  is  the  sealed  egg-cavity, 
the  lower,  the  open  feeding  puncture.  Figures  3  and  4  show  these  cavi- 
ties in  section,  enlarged.  Other  apple  curculio  punctures  are  shown  in 
figures  1  and  2,  Plate  12. 

With  one  exception  the  cavities  made  by  the  insects  observed  were  of 
practically  the  same  dimensions,  as  follows :  surface  opening,  .  03  inch  in 
diameter;  depth,  .12  inch;  greatest  diameter  of  enlarged  portion,  .08 
inch.  Most  of  the  excavations  were  nearly  cylindrical  at  the  surface  end, 
gradually  broadening  below,  with  the  egg-cavities  various  in  form.  The 
cavity  made  by  No.  3,  a  very  small  beetle,  was  only  .09  inch  deep, 
with  a  surface  opening  .02  inch  in  diameter. 

Oviposition  by  the  apple  curculio  does  not  necessarily  cause  the  fruit 
to  fall,  but  it  does,  as  a  rule,  completely  arrest  growth  at  the  point  punc- 
tured. Surrounding  parts  continue  to  develop  and  soon  the  sealed  open- 
ing appears  at  the  bottom  of  a  more  or  less  deep  depression.  Early  spring 
punctures  made  when  the  fruit  is  very  small  commonly  involve  the  ovary 
and  not  infrequently  the  ovules  are  eaten  out  and  the  egg  dropped  directly 
into  the  ovule  cavity.  Where  this  is  the  case,  marked  deformity  common- 
ly follows.  While  the  plugged  opening  is  left  in  a  depression,  it  is  at  the 


520 


BULLETIN     No.  98. 


PLATE   12.      FIG.    1—  EXTERNAL  APPEARANCE  OF  APPLE  CURCULIO  PUNCTURES 
FIG.  2 — SECTION  THROUGH  APPLE  CURCULIO  PUNCTURES. 


1905.]  THE   CURCULIO    AND  THE   APPLE.  521 

same  time  raised  away  from  the  core,  greatly  lengthening  the  channel 
leading  to  the  egg-cavity.  This  channel  may  become  one-half  inch  to 
more  than  an  inch  in  length,  and  in  long  section  appears  filled  with  brown, 
granular  matter,  or  as  is  frequently  the  case,  the  channel  is  completely 
closed  by  thick-walled  fruit  cells  and  appears  as  a  more  or  less  green  line 
that  is  compact  and  hard  in  texture.  Figures  1  and  2,  Plate  18,  illus- 
trate the  punctures  here  referred  to.  Egg  punctures  made  a  little  later 
in  the  season  when  the  apples  are  an  inch  or  more  in  diameter,  do 
not,  of  course,  reach  the  core,  but  they  produce  the  same  deformities, 
and  if  the  egg  hatches  and  the  larva  begins  development,  the  apple  is 
affected  to  such  an  extent  that  the  presence  of  the  developing  insect  can 
be  detected  with  considerable  certainty  by  external  appearances.  Be- 
sides the  deformity,  the  infested  fruit  appears  stunted  and  frequently 
more  or  less  shriveled.  After  the  beetles  leave  them,  these  apples  often 
become  dry  and  remain  on  the  tree  indefinitely.  An  exit  hole  of  the  apple 
curculio  in  a  small,  shriveled  and  dry  apple  is  shown  in  Fig.  2,  Plate  11. 
In  three  cases  beetles  were  observed  to  spend  more  than  one  hour  in 
excavating  egg-cavities,  and  then  walk  off,  without  depositing  eggs,  and 
begin  new  punctures.  In  one  case  a  beetle  completed  an  egg-cavity, 
turned  about,  and  deposited  an  egg  on  the  surface  near  the  opening,  then 
turning  again,  she  attacked  the  egg,  devoured  it,  and  after  racing  about 
the  fruit  for  a  short  time,  began  a  new  puncture.  Th'*  was  the  only  case 
of  egg-eating  seen,  but  if  the  practice  is  at  all  commo  ',  it  may  account 
for  some  of  the  many  empty  cavities  found. 

PERIOD   OF   OVIPOSITION.     NUMBER   OF   EGGS. 

During  the  season  of  1903,  no  definite  information  was  obtained  re- 
garding the  number  of  eggs  deposited,  and  but  little  was  learned  of  the 
length  of  the  period  over  which  oviposition  extended.  The  first  eggs 
were  found  May  13th,  the  last  July  9th.  In  the  two  weeks  following 
July  9th,  considerable  time  was  given  to  the  search  for  eggs,  or  beetles 
engaged  in  ovipositing,  but  none  were  found.  Beetles  were  occasionally 
found  resting  upon  apples,  but  there  were  no  evidences  of  any  attempt 
to  deposit  eggs.  The  conclusion  was  reached  that  oviposition  ceased 
about  the  middle  of  July,  and  that  the  duration  of  the  period  for  this 
work  was  about  sixty  days. 

In  the  spring  of  1904,  plans  were  laid  for  securing  more  definite  and 
detailed  information  regarding  the  period  for  egg  laying  and  number  of 
eggs.  In  furtherance  of  these  plans,  twenty  pairs  of  apple  curculios  were 
captured  as  early  in  the  season  as  they  could  be  found,  and  confined  in  the 
same  manner  as  were  the  plum  curculios  previously  mentioned.  Fresh 
apples  were  supplied 'daily,  at  6:30  in  the  morning  and  at  8:30  in  the 
evening.  The  punctured  apples  removed  were  examined ;  record  made  of 
eggs  and  punctures,  and  then  the  apples  were  placed  in  glasses  and  re- 


522  BULLETIN    No.  98.  [February, 

tained,  for  determination  of  the  period  of  development.  This  work  was 
continued  until  the  last  beetle  died,  August  14th.  The  data  accumu- 
lated have  been  brought  together  in  the  tabulation  on  page  523. 

PERIOD    OF   OVIPOSITION. 

The  first  egg  was  laid  May  23d,  the  last  July  22d,  so  that  the  egg  laying 
season  for  this  year  extended  over  sixty  days.  The  longest  time  between 
the  first  and  last  egg  for  any  individual  is  fifty-six  days  for  No.  8.  This 
insect  deposited  the  last  egg  July  22d,  and  died  July  27th.  Some  of  the 
insects  lived  a  much  longer  time  after  depositing  the  last  egg  than  did 
this  one,  for  example  No.  1.  This  insect  lived  until  August  14th,  eighty- 
seven  days  from  date  of  capture,  deposited  the  last  egg  June  23d,  but  did 
not  die  until  fifty-two  days  later.  Another,  No.  6,  was  in  confinement 
for  eighty-three  days,  laid  a  total  of  only  four  eggs,  the  last  June  2d,  and 
lived  for  seventy-two  days  beyond  this,  or  until  August  14th. 

This,  No.  6,  represents  one  extreme.  The  other  extreme  is  represented 
by  No.  2.  This  insect  deposited,  on  forty-eight  of  the  fifty-six  days  in 
confinement,  a  total  of  one  hundred  and  twenty-two  eggs.  There  were 
fifty-two  days  between  the  first  and  last  egg,  and  she  died  July  17th, 
within  twenty-four  hours  of  depositing  the  last  egg.  Some  of  the  averages 
for  the  twenty  females  are: 

Number  of  days  in  confinement 51 . 6 

Number  of  days  on  which  eggs  were  laid 27 . 9 

Number  of  days  between  first  and  last  egg 34 . 6 

NUMBER  OF   EGGS. 

The  total  number  of  eggs  recorded  was  1,316,  an  average  of  65.8  for 
each  female.  Individual  records  range  from  4  to  122.  Of  the  total 
number  of  eggs  laid,  799,  or  60.71  percent,  were  deposited  during  the  day 
period,  and  517,  or  39.29  percent,  during  the  night.  This  distribution  of 
oviposition  between  day  and  night  is  not  so  nearly  equal  as  with  the  plum 
curculio,  but  enough  eggs  are  laid  at  night  to  indicate  a  distinctly  noc- 
turnal habit. 

Departures  from  normal  procedure  in  oviposition  are  seen  in  the 
thirty-seven  egg  punctures  which  were  left  without  eggs,  and  in  the 
eighteen  eggs  laid  on  the  surface  of  the  fruit  and  not  accompanied  by 
egg  punctures.  These  eggs  on  the  surface  range  from  one  to  five  each  for 
nine  individuals.  They  were  all  laid  towards  the  end  of  the  egg  laying 
period,  and  were  probably  left  on  the  surface  because  of  inability  to  make 
the  punctures.  It  was  frequently  observed  that  old  beetles  experienced 
difficulty  in  breaking  the  skin  of  the  fruit.  This  may  have  been  because 
of  general  debility  from  age,  exceptional  smoothness  or  toughness  of  the 
fruit  skin,  accident  to  the  jaws,  or  the  loss  of  parts  of  one  or  more  of  the 
anterior  legs.  The  beak  of  the  apple  curculio  is  so  long  in  proportion  to 
the  body  that,  when  starting  punctures,  it  is  necessary  that  the  body  be 


1905.] 


THE   CtJRCULio  AND  THE  APPLE. 


523 


•s-inoq  ^-2  ui  saan^ound 
3mpaaj      jo     jaqumii     uinmixujv 


r-i  C1  C^  >-i  ^H  i-H        (M  1-1  CO  <N  <N  C<l  CO  (M  (M  (M  CO  CO  C< 


'W  '<*  08:8  '?^q 
sajn^aund  Suipaaj  jo  jaquin^j 


i-H  i-H  IM  • 


sajn^ound  Suipaaj   jo  aaqumf,j 


•saanjound  Sutpaaj  jo 


sajnjound 
3mpaaj  qoiqM  uo  sAep  jo  jaqinn 


•sanoij 


•w  VQS:9  Pa«  'w  '«!  08:8 
^aq   piB)  s33a  jo  jaquin^ 


iB|  s33a   jo 


COOO^HIOIM        CO  CO  CO  Tf  CO  (M  C^  •*  r}*  1C  fO  »O  CO  <N 


•saanjound  on 
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524  BULLETIN    No.  98.  \February, 

raised  as  high  above  the  fruit  as  the  length  of  the  legs  will  allow  (see 
Fig.  1,  Plate  11),  and  secure  anchorage  for  the  feet  is  necessary  in  order  to 
press  the  beak  against  the  fruit  with  sufficient  force.  On  fruit  that  is 
large  and  perfectly  smooth,  beetles  fail  to  secure  that  anchorage  for  the 
feet,  without  which  it  is  impossible  for  them  to  break  the  skin.  The  apple 
curculio  is  even  more  helpless  than  the  plum  curculio  in  this  regard. 

The  maximum  number  of  eggs  per  day  of  twenty-four  hours  varies 
from  one  to  six  for  the  different  insects,  and  the  average  maximum  is 
four  and  three-fourths.  This  is  considerably  below  the  average  maxi- 
mum for  the  plum  curculio ;  but,  as  the  apple  curculio  requires  more  time 
in  preparing  a  cavity,  probably  the  working  time  of  the  two  insects  for  an 
equal  period  would  not  be  very  different.  The  season  of  oviposition  for 
the  plum  curculio  is,  however,  considerably  longer  than  for  the  apple 
curculio. 

FEEDING    PUNCTURES. 

The  total  number  of  feeding  punctures  made  by  the  twenty  pairs  of 
apple  curculios  is  6,441.  Of  these,  3,948,  or  61.29  percent,  were  made 
during  the  day  period,  and  2,493,  or  38.71  percent,  during  the  night 
period.  These  percentages  are  in  close  accord  with  the  division  of  egg 
laying,  and  serve  to  confirm  the  fact  that  the  species  is  nocturnal  as  well 
as  diurnal. 

The  major  portion  of  the  feeding  punctures  are  made  by  the  male. 
It  would  seem  that  the  female,  who  eats  more  than  her  own  bulk  of  apple 
pulp  every  time  she  prepares  to  deposit  an  egg,  would  not  need  other  food, 
and  it  is  believed  she  seldom  makes  other  punctures  during  the  season  of 
oviposition.  She  does,  however,  sometimes  wholly  complete  egg-cavi- 
ties and  then  leave  them  without  placing  an  egg,  as  has  been  observed  on 
several  occasions. 

The  feeding  punctures  made  by  the  male  are  cylindrical,  vary  from 
.04  to  .08  inch  in  depth,  and  are  about  .04  inch  in  diameter.  The  time 
spent  on  each  puncture  varies  from  ten  to  fifteen  minutes,  and  sometimes 
two  or  three  are  made  with  but  very  short  intervals  of  time  between. 
These  feeding  punctures  generally  result  in  deformities  which  are  as  a  rule 
less  marked  than  are  those  caused  by  egg  punctures.  Sometimes  the 
tissue  surrounding  a  puncture  develops  in  such  manner  as  to  elevate  the 
puncture  above  the  surface  of  the  fruit,  and  it  appears  as  a  crater-like 
cavity  at  the  summit  of  an  elevation,  as  shown  at  (a)  Fig.  1  and  (a)  Fig.  2, 
Plate  12.  More  frequently  the  growth  of  the  surrounding  tissue  leaves  the 
original  puncture  at  the  bottom  of  a  more  or  less  contracted  deep  de- 
pression, as  shown  at  (c)  Plate  12.  Further  illustration  of  the  effects  of 
apple  curculio  punctures  is  given  in  Plate  13.  This  plate  is  from  a  photo- 
graph of  an  apple  picked  from  the  tree  August  20th.  The  apple  is  marked 
by  nine  apple  curculio  feeding  punctures,  eight  of  which  caused  deformi- 
ties; five  plum  curculio  feeding  punctures,  and  nine  plum  curculio  crescent 


1905. 


THE   (JuROULio   AND  THE   APPLE. 


525 


punctures,  a  total  of  twenty-three  punctures.  On  the  face  shown  in  the 
plate,  twelve  punctures  are  indicated.  Numbers  1,  2,  3,  4,  7,  and  9  are 
apple  curculio  feeding  punctures;  Numbers  5,  6,  8,  11,  and  12  are  plum 
curculio  crescent  punctures;  and  Number  10  is  a  plum  curculio  feeding 


PLATE  13.     DEFORMITIES  CAUSED  BY  THE  APPLE  CURCULIO. 

puncture.  The  egg-cavities  with  crescents,  5,  6,  and  12,  either  contained 
no  eggs  or  the  eggs  did  not  hatch.  Larvae  from  the  cavities  of  8  and  11 
bored  a  short  distance  and  died. 

THE  LARVA. 

The  larva  of  the  apple  curculio  is  footless,  dingy  or  yellowish  white 
in  color,  and  owing  to  enlargement  of  some  of  the  body  segments,  is  of 
curved  form  and  does  not  appear  able  to  straighten  out.  This  larva 
is  very  sluggish  in  movement,  but  as  it  pupates  in  the  cavity  eaten  out, 
ability  to  move  quickly  or  far  is  not  essential. 

Larvae  from  eggs  laid  early  in  the  season  feed  in  and  about  the  core 
because  eggs  deposited  in  the  very  small  apples  are  placed  close  to,  or, 
in  many  cases  directly  in,  the  core.  Those  from  eggs  laid  at  a  later  period 
when  the  apples  are  larger  remain  in  the  pulp;  often  they  simply  enlarge 
the  original  egg-cavity,  or  sometimes  they  eat  out  a  new  cavity  which 


526  BULLETIN    No.  98.  [February, 

connects  with  the  egg-cavity  by  a  small  opening.  A  pupa  in  a  cavity 
in  an  apple  is  shown  in  Fig.  3,  Plate  11. 

Several  determinations  made  to  within  a  fraction  of  a  day  show  that 
the  time  from  hatching  of  the  egg  to  the  full  development  of  the  larva 
is  from  nineteen  to  twenty-one  days.  The  average  time  in  the  larval 
stage  may  be  given  approximately  as  twenty  days.  Determinations  in 
the  same  manner  place  the  time  as  pupa  at  approximately  seven  days. 
Accurate  determinations  of  the  full  period  from  deposition  of  the  egg  to 
emergence  of  the  adult  or  beetle  form  were  recorded  for  three  hundred 
and  thirty-five  individuals,  and  range  from  twenty-seven  days  as  the 
minimum  to  the  maximum  of  forty-eight  days. 

Thirteen  individuals  emerged  in  the  shorter  period  of  twenty-seven 
days.  At  the  other  extreme,  one  appeared  on  the  forty-fourth,  one  on  the 
forty-seventh,  and  one  on  the  forty-eighth  day.  The  largest  number 
to  appear  on  any  day  was  fifty-eight,  on  the  thirty-first  day. 

During  the  ten  days,  twenty-seventh  to  thirty-sixth,  inclusive,  there 
emerged  three  hundred  and  ten,  or  92.54  percent  of  the  whole,  leaving 
only  twenty-five,  or  7.46  percent  coming  out  on  days  later  than  the 
thirty-sixth.  The  average  period  is  then  31.8  days,  or  practically  thirty- 
two  days.  The  first  beetles  to  emerge  came  out  June  30th,  the  last 
August  28th,  giving  a  period  of  emergence  of  sixty  days;  exactly  the  same 
as  the -period  of  oviposition.  By  months,  four,  or  1.19  percent,  emerged 
in  June,  two  hundred  and  ninety,  or  86.57  percent,  in  July  and  forty-one, 
or  12.24  percent  in  August. 

HABITS  OF  BEETLES  AFTER  EMERGENCE. 

Observations  made  during  the  season  of  1903  indicated  that,  unlike 
the  plum  curculio,  the  new  generation  of  the  apple  curculio  feed  upon 
apples  to  a  very  limited  extent,  after  emergence.  Beetles  coming  out 
in  breeding  cages,  although  constantly  supplied  with  fresh  apples,  made 
very  few  punctures,  but  remained  hidden  as  much  as  possible  under  any 
shelter  afforded.  In  1903  beetles  were  numerous  on  apples  in  the  orchard 
until  about  the  middle  of  July.  During  the  last  half  of  the  month  they 
became  quite  rare  and  after  the  first  of  August  none  were  found  upon 
the  trees.  Search  was  then  instituted  to  ascertain  where  the  beetles 
could  be  hiding.  On  August  18th,  eight  specimens  were  found  among 
leaves  on  the  ground  and  two  from  close  down  near  the  roots  in  blue-grass 
sod.  Other  specimens  were  taken  in  similar  situations  on  succeeding 
dates  up  to  October  2.  Their  food  habits  during  this  period  were  not 
determined,  but  they  did  not  feed  upon  apples.  During  the  season  of 
1904,  very  few  beetles  of  the  new  generation  were  taken  in  the  orchard. 
They  were  at  all  times  rare  as  compared  with  the  previous  season.  Fallen 
fruit  was  closely  picked  up  and  the  beetles  emerging  were  captured  in  the 


1905." 


THE  'CURCULIO   AND  THE  APPLE. 


527 


boxes  where  the  fruit  was  kept.     Some  emerged  from  apples  on  the  trees, 
but  no  evidence  of  feeding  upon  fruits  on  the  trees  was  found. 

In  the  laboratory,  five  pairs  of  newly  emerged  curculios  were  placed 
in  glasses  at  9:00  a.  m.,  July  4th,  and  with  each  pair  was  placed  an  apple; 
the  feeding  punctures  made  are  here  shown: 

DATES  OP  EXAMINATION. 


No. 

|o 

So 

rfj 

,s 

0* 

•^  •< 

1^ 

>>o 

i 

t§ 

.  •! 

Jj 

a- 

ll 

a 

10 

US 

^- 

• 

05 

* 

• 

UU 

1 
2 
3 
4 
5 

9 
13 
6 
5 
13 

18 
15 
22 
11 
29 

11 

12 
7 
10 
8 

23 
21 
19 
15 
8 

6 

10 
1 
2 

23 
25 
5 

8 
4 

7 

2 
1 

2 

1 

4 
2 

4 

2 

All  of  the  beetles  fed  freely  during  the  first  week.  Two  did  no  feeding 
after  the  tenth  day ;  only  one  fed  beyond  the  fifteenth  day.  No  punctures 
were  made  after  the  two  recorded  for  No.  1  July  22,  the  nineteenth 
day.  No  food  other  than  apples  was  supplied.  This  test  shows  that 
under  some  circumstances  beetles  do  make  feeding  punctures  after 
emerging,  but  we  have  no  evidence  that  they  ever  attack  apples  upon  trees. 

MORTALITY   DURING    DEVELOPMENT. 

The  twenty  pairs  of  apple  curculios  in  confinement  produced  1,316 
eggs.  Two  hundred  and  ninety-two  eggs,  or  a  little  more  than  22  per- 
cent, were  destroyed  in  examination,  so  that  the  apples  retained  for 
determination  of  the  period  of  development  contained  only  1,024  eggs. 
From  these  eggs,  three  hundred  and  forty-three  living  adults  were  reared. 
Eight  of  them  were  cut  from  the  fruits  and  are  not  included  in  the  record 
of  three  hundred  and  thirty-five  that  emerged  voluntarily. 

The  beetles  reared  represent  33^  percent  of  the  eggs,  and  the  loss 
during  development  is  therefore  66^  percent.  The  causes  of  this  heavy 
loss  are  not  all  apparent.  Some  eggs  failed  to  hatch;  larvae  died  at 
various  stages  of  development;  some  transformed  to  pupae  and  then 
died;  while  others  reached  the  adult  stage,  but  died  before  emerging. 
Loss  cannot  be  ascribed  to  predaceous  insects,  because  such  insects  were 
excluded.  Only  one  cause  is  definitely  known,  and  that  is  the  drying  up 
of  some  of  the  small  apples  early  in  the  season.  These  apples  became 
so  dry  and  hard  that  processes  of  insect  development  could  not  proceed. 
In  some  cases  where  single  apples  contained  five  or  six  eggs,  it  is  probable 
that  the  stronger  larvae  used  all  the  nourishment  and  that  the  weaker 
starved.  It  is  probable  also  that  some  individuals  were  weak  from  the 
beginning,  and  although  food  was  abundant,  had  not  sufficient  vitality 
to  complete  the  transformations.  During  the  season  of  1903,  consider- 


528  BULLETIN    No.  98.  [February, 

able  evidence  was  accumulated  that  pointed  to  strong  growth  of  the  fruit 
as  a  cause  of  mortality  among  apple  curculio  larvae  in  fruit  upon  the  trees. 
Many  of  the  egg-cavities  cut  into  were  found  to  be  more  or  less  completely 
filled  by  intruding  cell  masses.  These  cell  masses  were  quite  firm  in 
texture.  Sometimes  they  invaded  the  cavity  from  the  bottom,  but 
often  grew  as  wart-like  excrescences  from  small  areas  on  the  sides  of  the 
cavities.  In  several  instances,  dead  larvae  were  found  pressed  close  to 
the  cavity  wall  by  these  intruding  cell  masses. 

CHARACTERISTICS  OF  THE  TWO  SPECIES  OF 
CURCULIO  COMPARED. 

Comparing  the  damage  done  by  the  twO'Curculios  under  consideration 
it  is  quite  plain  that  for  northern  and  central  Illinois,  at  least,  much  the 
greater  injury  is  done  by  the  plum  curculio.  This  is  due  to  numerical 
superiority,  to  longer  period  of  work,  and  to  the  more  destructive  char- 
acter of  the  punctures  made.  The  greatest  damage  done  to  apples  by 
the  plum  curculio  is  done  after  all  injurious  work  by  the  apple  curculio 
has  ceased. 

During  the  season  of  oviposition,  when  insects  are  upon  the  trees,  the 
apple  curculio  is  much  less  timid  than  is  the  plum  curculio.  It  allows 
close  approach  without  appearing  disturbed,  while  the  plum  curculio  when 
approached  will  at  once  seek  a  hiding  place.  The  apple  curculio  is  not 
so  partial  to  dense  shade,  it  endures  strong  light  better,  and  is  less  given 
to  hiding  from  sight.  It  has  not  the  protective  instinct  of  folding  its 
legs  and  dropping,  which  is  so  characteristic  of  the  plum  curculio,  al- 
though it  occasionally  does  fall,  and  is  taken  in  jarring  over  a  sheet.  A 
characteristic  position  taken  by  the  apple  curculio  when  disturbed  is 
shown  in  Plate  14.  The  apple  curculio  more  readily  takes  wing  than 
does  the  plum  curculio.  This  we  have  tested  many  times,  always  finding 
the  plum  curculio  very  reluctant  to  fly,  either  by  day  or  by  night,  while 
the  apple  curculio  will  usually  attempt  flight  rather  than  crawling  off  to 
hide.  On  two  occasions,  while  jarring  over  a  sheet,  apple  curculios  have 
been  observed  to  fall,  spread  the  wings  and  fly  before  reaching  the  sheet. 
In  flight,  the  apple  curculio  takes  a  straight  course  and  flies  with  only 
moderate  speed.  The  plum  curculio,  in  all  cases  observed,  took  a  zigzag 
course  and  traveled  at  high  speed.  It  has  been  shown  by  records  made 
during  the  past  summer  that  both  species  are  to  quite  a  degree  nocturnal 
in  habits,  so  far  as  oviposition  and  feeding  are  concerned.  Results  of 
attempts  to  ascertain  habits  of  movements  at  night  were  not  sufficiently 
decisive,  but  indicate  in  a  general  way  that  the  plum  curculio  does  fly 
at  night.  In  the  summer  of  1903,  when  the  beetles  were  especially  abun- 
dant, two  trap  lanterns  were  used  for  several  weeks.  The  only  curculio 
caught  was  an  apple  curculio,  probably  an  accidental  catch.  Neither 


1905.]  THE   CURCULIO   AND  THE  APPLE.  529 

species  fly  to  light.  From  July  17th  to  August  24th,  several  sheets  of 
"Tangle-foot"  fly-paper  were  suspended  in  trees  to  be  examined  morning 
and  evening.  In  this  way  eighty-two  plum  cruculios  and  one  apple  cur- 
culio  were  caught.  Of  the  plum  curculios,  sixty-nine  were  caught  during 
the  night  period  and  thirteen  during  the  day  period.  Examinations, 
however,  were  not  made  at  perfectly  regular  hours,  and  there  was  always 
a  period  of  daylight  before  the  morning  examination-  and  after  the  eve- 


PLATE  14.     APPLE  CURCULIO  ON  APPLE,  POSITION  WHEN  DISTURBED.       x  3^. 

ning  examination,  so  that  we  do  not  regard  the  recorded  division  of  the 
catch  as  absolutely  correct.  But  making  all  due  allowances,  there  was 
evidently  a  greater  number  of  .plum  curculios  on  the  wing  at  night  than 
in  the  daytime.  This  conclusion  is  confirmed  by  one  specific  instance— 
the  sheets  examined  at  dark  and  again  in  the  early  morning  gave  a  catch 
of  nine  plum  curculios.  The  highest  number  for  any  day  period  was 
three.  Readiness  to  take  wing  was  also  tested  at  night  by  use  of  a  bulls- 
eye  lantern.  Search  for  beetles  was  made  between  the  hours  of  nine  and 
ten  on  a  dark  night;  thirteen  plum  curculios  were  found  resting  on  apples. 
Whenever  the  glare  of  light  was  directed  upon  a  beetle,  it  quickly  moved 
around  the  fruit  into  the  shade ;  following  with  the  light  simply  kept  the 
beetle  moving;  in  no  case  was  flight  induced,  although  in  some  instances 
beetles  were  followed  by  the  glare  of  light  for  several  minutes. 

Tests  of  willingness  to  fly  by  day  were  also  made  with  much  the  same 


530  BULLETIN    No.  98.  \February, 

result.     No  amount  of  badgering  induced  flight;  they  would  either  drop 
or  try  to  avoid  the  annoyance  by  crawling  away. 

The  plum  curculio  is  erratic  about  dropping  when  jarred.  Sometimes 
beetles  are  seen  to  drop  upon  being  approached  and  before  a  leaf  of  the 
tree  is  disturbed ;  sometimes  the  lightest  touch  upon  an  adjacent  branch 
will  cause  them  to  fall,  and  again  they  will  cling  on  through  severe  jarring. 
tn  one  instance  a  small  branch  was  grasped  in  hand  about  one  foot  below 
an  apple  on  which  a  beetle  was  resting.  The  branch  was  then  given  a 
quick  blow  with  a  lead  pencil,  between  the  hand  and  the  apple.  The 
beetle  made  no  movement.  Blows  were  repeated  at  short  intervals.  At 
the  fifth  stroke  the  legs  were  drawn  in  close  to  the  body,  and  the  beetle 
assumed  the  position  shown  in  Fig.  3,  Plate  2.  No  further  evidence  of 
disturbance  was  seen  until  the  eighteenth  blow  was  struck,  then  hold  of 
the  fruit  was  released  and  the  beetle  fell.  This  test  was  repeated  many 
times,  and  if  the  beetle  did  not  fall  when  the  branch  was  taken  in  hand, 
sometimes  one,  or  more  frequently  six  or  eight  blows  were  required  to 
dislodge  it. 

REPRESSION. 
MEANS  OF  CONTROLLING  CURCULIOS. 

What  remedies  possessing  the  qualities  of  efficiency,  ease  of  application, 
and  reasonable  cost  may  be  used  against  our  two  species  of  curculios? 
This  is  an  important  question,  and  one  upon  which  various  opinions  have 
been  expressed. 

Jarring  over  sheets  spread  under  trees,  the  old  and  still  standard  rem- 
edy for  plum  curculio  on  plums  and  cherries,  while  possible  in  young 
apple  orchards  just  coming  into  bearing,  cannot  be  recommended  as  prac- 
ticable for  orchards  of  commercial  extent. 

This  method  was  thoroughly  tested  during  the  season  of  1903  on  trees 
sixteen  years  of  age,  using  a  sheet  twenty-four  feet  square.  The  ac- 
companying Plate  (No.  15)  illustrates  this  sheet  in  use. 

Our  average  catch  per  tree  up  to  July  first  was  seventeen  plum  cur- 
culios and  one  apple  curculio  at  each  visit.  As  many  as  sixty  plum  cur- 
culios were  taken  at  one  time  from  a  single  tree,  but  the  trees  were  too 
rigid  to  be  properly  jarred,  and  the  spread  so  great  that  a  sheet  of  sufficient 
size  is  not  easily  handled  from  tree  to  tree. 

REPELLENTS. 

Growers  of  plums  and  cherries  many  years  ago  tried  various  repel- 
lents, such  as  burning  sulphur  and  coal  tar,  sprinkling  with  whale-oil 
soap,  or  soap  and  tar,  and  dusting  with  plaster,  air-slaked  lime,  or  car- 


1905. 


THE   CURCULIO   AND  THE   APPLE 


531 


532  BULLETIN    No.  98.  [February, 

bolized  lime.  Transactions  of  various  horticultural  societies  contain  re- 
ports of  the  successful  use  of  these  repellents,  but  adverse  reports  are  in 
the  majority,  and  the  fact  that  these  remedies  have  not  come  into  general 
use  is  sufficient  evidence  that  they  are  ineffective. 

ARSENICAL   POISONS. 

Spraying  with  arsenical  poisons  has  been  the  subject  of  experiments 
during  the  last  twenty  years.  Results  of  reported  experiments  have  been 
various,  but  in  the  main  favorable.  While  some  have  been  entirely  un- 
successful in  diminishing  the  amount  of  injury,  most  have  reported  vary- 
ing degrees  of  benefit.  As  high  as  75  percent  of  possibly  injury  controlled 
is  reported  in  one  or  two  cases.  No  one  has  claimed  perfect  success,  but 
in  several  cases  the  benefit  has  been  sufficient  to  warrant  commending  the 
use  of  arsenites  to  the  fruit-growers.  Most  of  those  who  have  experi- 
mented with  the  arsenites  have  worked  upon  stone  fruits,  and  the  most 
common  recommendation  is  to  jar  and  supplement  this  with  spraying. 

G.  C.  Brackett  reports  *  that  check  trees  gave  as  large  a  percent  of 
sound  fruit  as  did  trees  thoroughly  sprayed  with  London  Purple. 

Prof.  C.  M.  Weed,  from  experiments  on  cherries,  concludes,!  "First, 
that  about  three-fourths  of  the  cherries  liable  to  injury  by  the  plum  cur- 
culio  can  be  saved  by  two  or  three  applications  of  London  Purple.  Second, 
that  a  sufficiently  large  proportion  of  the  plum  crop  can  be  saved  by  the 
same  treatment  to  insure  a  good  yield  when  a  fair  amount  of  fruit  is  'set.' " 

Prof.  A.  J.  Cook  says,J  "I  believe  I  am  justified  in  the  conclusion  that 
spraying  with  the  arsenites  will  never  become  a  satisfactory  remedy  for 
the  work  of  curculio." 

The  earliest  and  most  complete  experiments  with  arsenites  for  curculio 
injury  to  the  apple  were  those  conducted  by  Professor  Forbes  in  1885,  and 
reported  in  the  transactions  of  the  Illinois  State  Horticultural  Society  for 
that  year.  In  the  experiments,  five  trees  were  sprayed,  and  for  each 
sprayed  tree  a  check  was  retained  for  comparison.  Two  trees,  sprayed 
eight  times  with  Paris  green  between  June  9th  and  September  3d,  had 
27.3  percent  of  the  fruit  punctured  by  curculios,  while  the  corresponding 
check  trees  showed  51.3  percent  of  injury.  During  the  same  period, 
eight  applications  of  London  Purple  were  made  to  one  tree,  which  on  final 
count  of  fruit  gave  39  percent  punctured,  while  the  fruit  of  the  check  tree 
showed  48  percent.  Two  trees  were  sprayed  with  lime  water,  and  of  this 
treatment  Professor  Forbes  says,  "While  producing  some  effect  on  the 
curculios,  lessening  the  damage  seemingly  about  one-fourth,  lime  is  less 

*Insect  Life,  December,  1888,  page  193. 

t  Proceedings  of  the  Society  for  the  Promotion  of  Agricultural  Science,  1889, 
page  107. 

J  Proceedings  of  the  Society  for  the  Promotion  of  Agricultural  Science,  1890,  23. 


1905.]  THE   CURCULIO  AND  THE  APPLE.  533 

efficient  in  this  respect  than  Paris  green."  Again,  in  conclusion,  "Fur- 
thermore, if  we  must  judge  from  results  thus  far  reached,  these  various 
applications  are  of  too  slight  effect  upon  the  apple  and  plum  curculios 
to  make  them  worthy  of  use  against  these  insects ;  Paris  green  diminishing 
curculio  blemishes  less  than  one-half,  London  Purple  about  one-fifth,  and 
lime  not  far  from  one-fourth." 

SPRAYING  EXPERIMENTS  AT  BARRY  IN  1903. 

When  this  investigation  of  curculio  injury  was  commenced  in  the  spring 
of  1903,  one  of  the  first  things  done  was  to  select  blocks  of  trees  for  treat- 
ment by  spraying  with  arsenical  poisons.  .  Two  blocks  of  sixty  trees  each 
were  selected.  One  was  in  the  orchard  of  Mr.  J.  R.  Williams;  the  other, 
twenty  rods  distant,  in  the  adjoining  orchard  of  Mr.  Albert  Blair.  Both 
orchards  were  planted  the  same  year,  and  were  at  this  time  (1903)  eighteen 
years  old.  The  trees  stood  twenty-four  by  twenty-eight  feet,  and  so  com- 
pletely did  they  cover  the  ground  that  passage  between  them  was  difficult. 
In  the  Williams  orchard,  blue-grass  sod  covered  a  considerable  portion  of 
the  ground,  and  the  surface  mulch  of  leaves  and  dead  grass  was  heavy. 
In  the  Blair  orchard,  the  trees  were  not  so  large,  branches  not  so  thickly 
interlaced,  and  passage  between  trees  less  obstructed.  The  ground  was 
covered  with  a  scattering  growth  of  plants,  representing  a  number  of 
species,  including  several  grasses,  but  there  was  no  established  sod.  Dead 
leaves  and  grass  were  less  abundant,  and,  in  general,  the  ground  was 
cleaner,  affording  less  favorable  hiding-places  for  insects  than  did  the 
Williams  orchard. 

The  blocks  of  trees  were  divided  into  six  plats  each,  as  shown  in  the 
diagrams  on  pages  534  and  535. 

The  plats  were  of  ten  trees  each,  except  that,  owing  to  vacancies,  the 
check  plat  in  each  block  (plat  3)  contained  only  eight  trees,  and  plat  6  in 
the  Williams  orchard  was  reduced  in  like  manner  to  eight  trees. 

In  order  to  control  in  some  degree  apple  scab  and  reduce  as  far  as 
possible  the  injury  from  codling  moth,  it  was  determined  that  all  trees  of 
both  blocks  should  receive  three  early  applications  of  Bordeaux  mixture 
and  Paris  green.  Following  the  third  spraying,  plats  1,  2,  and  4  of  each 
block  were  to  receive  a  varying  number  of  applications  of  Paris  green. 
Plat  3  of  each  block  was  to  be  retained  as  a  check,  and  given  no  further 
spraying.  The  plats  numbered  "5"  were  to  be  treated  with  arsenite  of 
lime  and  those  numbered  "6"  with  arsenate  of  lead.  A  definite  schedule 
was  prepared  on  the  plans  as  outlined  above,  and  was  closely  followed 
throughout  the  season.  The  number  of  applications  each  plat  received, 
with  formulae  and  dates  of  application,  is  given  below: 


534  BULLETIN    No.  98.  [February, 


o  opigso  o 
ooooo 


oooo  o 

PLAT  5 

ooooo 


o  o  oo  o 

PLAT-* 

OOOOO 


oo     o  o 

PL  AT  3 

ooo 


ooooo 

O  OT)  O  O 


ooooo 

PLAT  1 

ooooo 


ORCHARD 

or  w. 

ALBERT  E>LAii2. 

'.ILLINOIS,  s 


PLATE  16. 


1905.] 


THE   CURCULIO   AND  THE  APPLE. 


535 


PLAT   I 


PLAT 


PLAT  3 


ooooo 


PLAT 


PLAT  5 


PL  AT  6 


ORCHARD 
or 

I  E.WILLIAMS 

'.ILLINOIS. 


w. 


PLATE  17. 


536  BULLETIN    No.  98.  [February, 

TREATMENT   OF   PLATS   FOR   CURCULIO. 

Orchards  of  Albert  Blair  and  John  R.  Williams,  Barry,  Pike 
County.     Season    of    1903. 

All  plats  were  given  three  applications  for  scab  and  codling  moth,  us- 
ing Bordeaux  mixture  and  Paris  green.  Formula,  4  4  ^-50. 

First,  when  buds  were  bursting April  15th  and  16th. 

Second,  just  after  petals  had  fallen May  4th  and  5th. 

Third,  one  week  later May  12th. 

Plat  1. — This  plat  was  sprayed  once  each  week  from  May  15th  to 
July  31st,  and  was  given  a  final  application  two  weeks  later  on  August 
15th.  The  dates  of  application  were  May  15th,  22d,  29th;  June  5th, 
12th,  19th,  26th;  July  3d,  10th,  17th,  24th,  31st;  August  15th. 

The  material  used  was  Paris  green,  %  lb.;  lime,  6  Ibs.;  water  50 
gallons. 

The  number  of  applications  was  thirteen,  which,  with  the  three  ap- 
plications of  Bordeaux  mixture  and  Paris  green,  makes  a  total  of  sixteen. 

Plat  2. — This  plat  was  sprayed  on  dates  as  given  below,  using  the 
same  formula  as  used  on  plat  1;  May  15th,  22d;  June  15th;  July  6th, 
27th;  Aug.  17th;  September  7th. 

Seven  applications  were  given,  or,  adding  the  three  early  applications, ' 
a  total  of  ten. 

Plat  3. — Check,  no  spray  after  May  12th. 

Plat  4. — This  plat  was  sprayed  with  the  same  formula  used  for  plats 
1  and  2,  on  May  15th,  22d;  June  15th;  July  6th,  28th;  five  times,  or, 
adding  early  applications,  a  total  of  eight. 

Plat  5. — Arsenite  of  lime  was  applied  to  this  plat  four  times  as  follows — 
May  23d;  June  6th,  20th;  July  6th. 

The  formula  used  was — White  arsenic,  2  oz.;  sal  soda,  Y^  lb.;  lime, 
4  lb. ;  water,  50  gallons. 

Add  the  three  applications  of  Bordeaux  and  Paris  green  to  the  four  of 
arsenite  of  lime  and  we  have  a  total  of  seven  applications. 

Plat  6. — This  plat  was  sprayed  with  arsenate  of  lead  made  on  the  fol- 
lowing formula — Lead  acetate,  12J/4  oz.;  soda  arsenite,  5  oz.;  water, 
50  gallons. 

Four  applications  were  made,  May  23d;  June  6th  and  20th;  and  July 
6th.  The  total  number  of  applications  is  seven,  the  same  as  for  plat  5. 

The  spraying  outfit  used  for  the  early  applications  was  a  "Noxall" 
250  gallon  tank  on  which  was  mounted  a  Gould  "Monarch"  pump. 
Two  lines  of  hose,  each  thirty  feet  long  with  Bamboo  extension  rods 
twelve  feet  long  fitted  with  double  Vermorel  nozzles  completed  the 
outfit.  Careful  attention  was  given  to  the  agitation  of  the  mixtures, 
Nozzle  caps  with  openings  of  the  smallest  size  were  used,  and  as  high 
pressure  as  is  possible  with  the  hand  pump  was  maintained.  The  quan- 


PLATE    18 

1  Apple  curculio  egg  puncture,  showing  how  channel  has  lengthened  with  growth  of  apple. 

2  Another  example  of  apple  curculio  puncture. 

3  Showing  a  crescent  mark  where  egg  has  failed  to  hatch;  the  mark  has  grown  out, 

leaving  a  russet  spot  as  a  surface  blemish. 


1905.]  THE   CURCULIO   AND  THE  APPLE.  537 

tity  of  material  sprayed  upon  each  tree  was  approximately  three  gallons 
at  each  application.  For  later  applications,  where  only  one  or  two  plats 
in  each  block  were  sprayed  at  a  time,  the  hose  was  coupled  to  a  "Spray- 
motor"  pump  mounted  on  a  fifty-gallon  barrel.  This  outfit  was  as  effec- 
tive as  the  other,  and  was  used  because  more  easily  portable.  Constant 
care  was  exercised  to  secure  even  distribution,  and,  in  general,  to  do 
the  work  in  the  best  possible  manner.  A  slight  spotting  of  foliage  fol- 
lowed some  of  the  later  applications  of  Paris  green,  but  the  injury  was 
not  serious. 

Cultivation  and  breaking  up  of  sod  on  the  plats  began  about  June 
20th.  For  this  purpose,  two  "Clark's  Cutaway  Harrows"  were  provided, 
one  of  which  was  extended  by  means  of  an  oak  plank  to  a  spread  of  six- 
teen feet.  This  arrangement  made  possible  the  cutting  of  sod  close  to 
the  tree  trunks.  After  these  tools  had  gone  over  the  ground  several  times, 
a  toothed-harrow  was  used  to  smooth  the  surface.  These  operations 
were  repeated  at  intervals,  until  the  surface  was  free  from  all  vegetation. 
In  July  the  ground  under  the  trees  was  raked  smooth  in  order  to  facilitate 
the  gathering  of  fallen  fruit. 

Windfalls  were  gathered  nine  times  during  the  season.  Each  lot 
of  fruit  gathered  was  carefully  examined  and  record  made  of  curculio 
punctures.  The  dates  of  gathering  were  as  follows:  June  18th,  19th; 
June  26th,  27th;  July  3d,  4th;  July  21st,  22d;  July  28th,  29th;  Au- 
gust 10th,  llth;  August  28th,  29th;  September  llth,  12th;  and  October 
1st  and  2d. 

October  1st  and  2d,  the  fruit  remaining  on  the  trees  was  picked, 
examined,  and  record  of  punctures  made,  as  with  the  faHen  fruit. 

RESULTS. 

On  final  computation,  it  was  found  that  a  total  of  29,943  apples  had 
been  gathered  and  examined.  Of  these,  25,363,  or  84.7  percent  were 
gathered  from  the  ground,  and  4,580,  or  15.3  percent  were  picked  from 
the  trees.  The  following  tabulations  show  the  numbers  and  percent  of 
punctured  and  puncture-free  apples  taken  from  each  plat  in  each  of  the 
two  blocks. 

DISCUSSION  OF  RESULTS. 

A  glance  at  the  tabulations  given  discloses  the  fact  that,  so  far  as 
any  favorable  results  are  concerned,  our  labor  of  spraying  was  thrown 
away.  Spraying  in  this  instance  did  not  control  curculio  injury.  Ap- 
parently, frequent  spraying  had  some  influence,  because  the  percentage 
of  uninjured  apples  from  the  plats  receiving  sixteen  applications  is  a 
little  higher  than  for  any  other  plats,  but  the  differences  are  too  small  to 
warrant  any  claim  of  real  benefit.  During  the  season,  the  fruit  on  the 
sprayed  plats  and  on  the  trees  in  all  other  parts  of  the  orchards  was 
critically  examined  many  times,  and  at  no  time  could  there  be  detected 
any  diminution  of  injury  that  might  be  attributed  to  the  spray  applied. 


538 


BULLETIN    No.  98.  [February, 

ORCHARD  OF  J.  R.  WILLIAMS,  BARRY,  1903. 


No. 
of 
Plat. 

Total  fruits 
picked 

Total  fruits 
windfalls. 

Total. 

Grand 

total. 

Percent 
punctured. 

Percent 
not  punctured. 

1 
c 

3 
ft 

•d 

V 
3 

•d 
£ 

3 

0 

a 

•d 

Z  o 
3 

1 

3 

o 
C 

«.! 

c 

EL 

I 
II 
III 

IV 
V 
VI 

880 
415 
411 
742 
657 
413 

36 
22 
10 
29 
43 
8 

3021 
1767 
2491 
3630 
6094 
3696 

182 
81 
27 
69 
93 
88 

3901 
2182 
2902 
4372 
6751 
4109 

218 
103 
37 
98 
136 
96 

4119 
2285 
2939 
4470 
6887 
4205 

94.71 
95.49 
98.74 
97.81 
98.03 
97.72 

5.29 
4.51 
1.26 
2.19 
1.97 
2.28 

Total 

3518 

148 

20699 

540 

24217 

688 

24905 

97.24 

2.76 

3,666  apples,  or  14.72  percent,  were  picked  from  the  trees. 
21,239  apples,  or  85.28  percent,  were  windfalls. 

ORCHARD  OF  ALBERT  BLAIR,  BARRY,  1903. 


No. 
of 
Plat. 

Total  fruits 
picked. 

Total  fruits 
windfalls. 

Total. 

Grand 
total. 

Percent 
punctured. 

Percens 
not  punctured. 

•d 
£ 

3 
O 
C 

£ 

•d 
^£ 

^  c 

3 

1 

0 

§ 

3 

«i 

B 

C. 

1 

c 

£ 

•d 
a 

I 
II 
III 

IV 
V 
VI 

118 
100 
67 
151 
106 
281 

24 
19 
11 
15 
12 
10 

399 
330 
234 
459 
688 
1746 

75 
30 
22 
48 
50 
43 

517 
430 
301 
610 
794 
2027 

99 
49 
33 
63 
62 
53 

616 
479 
334 
673 
856 
2080 

83.93 
89.77 
90.12 
90.64 
92.76 
97.45 

16.07 
10.23 
9.88 
9.36 
7.24 
2.55 

Total 

823 

91 

3856 

268 

4679 

359 

5038 

92.87 

7.13 

914  apples,  or  18.91  percent,  of  total  fruits  were  picked  from  trees. 
4,124  apples,  or  81.06  percent,  of  total  fruits  were  windfalls. 

The  materials  used  in  spraying  were  known  to  be  of  the  best  obtainable, 
and  no  fault  could  be  found  with  the  thoroughness  of  the  applications. 
The  experiments  were  reasonably  extensive,  and  the  spraying  dates 
covered  practically  the  whole  season. 

In  considering  possible  reasons  for  the  results  obtained,  there  appear, 
three  factors  of  undoubted  influence. 

First. — Weather  conditions  of  early  spring  and  their  bearing  upon 
the  crop. 

Second. — Location  of  the  plats  treated  in  the  midst  of  large  orchards. 
These  orchards  are  at  several  points  contiguous  to  tracts  of  native  wood- 
land in  which  hawthorn,  wild  crab,  and  wild  plum,  native  food  plants 
of  curculios,  are  abundant. 

Third. — Unusual  abundance  of  the  insects. 

The  weather  of  early  spring  was  mild  and  buds  pushed  forward  rap- 


1905.]  THE   CURCULIO   AND  THE  APPLE.  539 

idly.  April  15th  blossom  clusters  were  open,  and  April  22d  most  trees 
were  in  full  bloom.  Then  came  a  period  of  cloudy  weather,  with  fre- 
quent cold  rains,  continuing  until  May  1st  and  followed  on  that  date  by 
a  severe  freeze.  Blossoms  and  young  fruits  fell  rapidly,  and  few  were 
left  upon  the  trees.  The  small  average  product  per  tree  can  be  judged 
from  the  totals  of  fruit  gathered,  as  shown  in  the  preceding  tabulations. 
This  scarcity  of  fruit  is  certainly  in  some  measure  responsible  for  the  high 
percentage  punctured. 

The  possible  influence  of  the  second  factor,  the  location  of  the  plats 
in  the  midst  of  large  orchards,  was  appreciated  and  discussed  before 
work  began,  but  there  appeared  no  possible  way  of  changing  conditions 
in  this  respect.  Curculios  are  winged  insects.  They  fly.  We  may 
suppose  that  all  curculios  infesting  a  block  of  trees  chosen  for  treatment 
are  killed  by  applications  of  arsenical  poisons;  there  is  nothing  to  prevent 
invasion  by  a  new  army  of  insects  from  surrounding  untreated  trees, 
and  this  might  go  on  indefinitely  through  the  season.  Practically,  we 
know  nothing  of  how  many  curculios  were  killed  by  poisons  applied,  nor 
do  we  know  to  what  extent  the  suggested  movement  of  curculios  from 
untreated  to  treated  trees  took  place.  We  do  know  that  during  the  whole 
season  the  insects  were  very  abundant  on  both  treated  and  untreated 
trees. 

The  third  factor  tending  to  raise  the  percentages  of  injury  done,  is 
the  excessive  abundance  of  the  curculios.  The  year  previous,  1902, 
was  a  year  of  abundant  fruit.  The  insects  were  undisturbed  throughout 
the  season.  They  multiplied  enormously  and  hibernated  through  a  mild 
winter;  hence  their  abundance  in  1903.  This  abundance  is  illustrated 
by  the  fact  that  plum  curculios  needed  for  laboratory  purposes  were 
gathered  by  simply  picking  them  from  apples  while  feeding,  ovipositing, 
or  resting.  There  was  never  any  trouble  in  obtaining  plenty  in  this 
manner.  Early  in  the  season,  the  apple  curculios  were  taken  in  the  same 
way,  but  later  they  became  rare,  and  late  in  July  entirely  disappeared. 

The  percentages  of  punctured  fruit  on  the  treated  and  check  plats,  as 
given  in  the  tabulations,  afford  no  evidence  that  any  curculios  died  from 
poison.  We  do  not  know  whether  the  arsenites  applied  killed  many,  few, 
or  none.  One  attempt  was  made  to  gain  information  on  this  point.  A 
tree  bearing  considerable  fruit,  located  outside  our  treated  blocks,  was 
sprayed  heavily  with  Paris  green.  Immediately  afterwards  a  sheet, 
24  x  24  feet,  was  spread  underneath,  and  examined  twice  daily  for  eleven 
days.  It  was  thought  that  if  curculios  took  the  poison  they  would  become 
sick  and  fall  upon  the  sheet  below.  Results  were  entirely  negative.  On 
first  examination,  two  living  and  apparently  healthy  apple  curculios  were 
found.  The  fourth  day  three  living  and  active  plum  curculios  were  taken. 
Subsequent  examinations  yielded  nothing.  No  dead  or  ill  curculios  were 
at  any  time  found.  To  be  sure,  there  may  be  error  in  supposing  that 


540  BULLETIN    No.  98.  [February, 

poisoned  curculios  would  fall.  They  may  cling  in  death  agony  to  the  tree, 
or,  on  experiencing  the  first  pangs,  take  wing  and  fly  away.  Again, 
some  might  fall  and  be  devoured  by  birds  or  insects  in  the  intervals  be- 
tween examinations.  In  spite  of  these  considerations,  the  most  probable 
reason  why  no  dead  curculios  were  found  is  because  none  were  killed. 

Laboratory  experiments  show  that  Paris  green  will  kill  curculios,  as  it 
will  any  animal  life,  if  taken  internally  in  sufficient  quantity.  The  great 
difficulty  is  in  administering  a  sufficient  dose  to  insects  that  in  the  early 
part  of  the  season  disturb  so  small  a  portion  of  fruit  surface  in  their  feeding 
and  oviposition.  In  an  experiment  carried  through  by  Mr.  J.  R.  Shinn, 
one  apple  was  treated  with  a  mixture  of  Paris  green  and  water  at  the  rate 
of  four  ounces  to  fifty  gallons ;  a  second  with  a  similar  mixture  at  the  rate 
of  eight  ounces  to  fifty  gallons;  a  third  with  twelve  ounces  to  fifty  gallons; 
and  a  fourth  with  sixteen  ounces  to  fifty  gallons.  These  apples  were 
placed  in  separate  jars,  and  in  a  fifth  jar  was  placed  an  untreated  apple. 
Ten  plum  curculios  were  placed  in  each  jar.  In  the  jar  containing  the 
apple  treated  with  four  ounces  to  fifty  gallons  three  were  dead  in  four 
hours,  five  were  dead  at  the  end  of  six  hours ;  no  further  fatalities  resulted 
until  the  fourth  day,  when  one  more  died,  and  all  were  dead  at  the  close 
of  the  fifth  day.  The  next  stronger  mixture  gave  but  slightly  different 
results.  Two  were  dead  in  two  hours,  and  five  at  the  end  of  eleven  hours. 
At  the  end  of  the  fourth  day,  seven  were  dead.  One  more  died  on  the 
fifth  day,  and  the  two  remaining  on  the  seventh  day.  Of  the  lot  confined 
with  the  apple  treated  with  twelve  ounces  to  fifty  gallons,  one  died  in 
seven  hours,  six  were  dead  at  the  end  of  eleven  hours,  and  all  were  dead 
at  the  end  of  the  third  day.  Where  the  apple  was  treated  with  the  mix- 
ture of  one  pound  to  fifty  gallons,  all  beetles  died  within  twenty-four  hours. 
Of  the  beetles  confined  with  the  untreated  apple,  one  died  on  the  fifth  day, 
and  eight  were  dead  at  the  end  of  the  seventh  day.  From  the  mortality 
here  shown,  we  may  infer  that  some  at  least  of  the  later  deaths  in  the 
other  jars  were  due  to  natural  causes,  and  not  to  the  poison. 

The  results  of  this  experiment  simply  indicate  that  if  Paris  green  is 
applied  and  its  presence  maintained  in  sufficient  quantity,  so  that  the 
curculios  are  sure  to  take  it  when  making  punctures,  we  may  be  quite 
sure  of  good  results  in  the  destruction  of  the  plum  curculios. 

With  the  apple  curculio,  however,  results  derived  from  a  single  test 
are  not  so  promising.  Two  apples  treated  with  Paris  green  in  water  at 
the  rate  of  one  pound  to  fifty  gallons  were  placed  in  separate  jars.  In 
one,  ten  plum  curculios  were  placed;  in  the  other  ten  apple  curculios. 
The  plum  curculios  were  all  dead  at  the  end  of  ten  hours.  At  the  end  of 
six  days  the  apple  curculios  were  all  living,  and  to  all  appearances  in  good 
health.  This  result  strengthens  a  conviction  derived  from  observation, 
that  the  apple  curculio  eats  very  little,  if  any,  of  the  skin  of  the  fruit. 
The  punctures  they  make  are  minute.  The  skin  is  torn  up,  but  commonly 


PLATE    19 

1  Ben  Davis  apple,  showing  late  feeding  punctures  of  plum  curculio.     Natural  size. 

2  Section  of  the  apple,  showing  section  of  one  of  the  punctures.     Natural  size. 

3  The  puncture  of  Figure  2  enlarged. 


1905.]  THE   CURCULIO   AND  THE  APPLE.  541 

the  torn  particles  are  no*  detached.  Often  in  watching  beetles  at  work  it 
has  been  observed  that  the  torn  particles  of  skin  stand  erect  as  a  sort  of 
fringe  about  the  beak  at  the  point  of  insertion.  On  withdrawal  of  the 
beak,  this  broken  skin  sometimes  falls  back  over  the  opening,  completely 
closing  it. 

No  doubt  apple  curculios  sometimes  eat  small  particles  of  apple  skin, 
but  the  quantity  is  so  minute  that  the  chances  of  taking  in  poison  that  has 
been  distributed  over  the  surface  are  very  remote. 

Plum  curculios  are  much  more  voracious  feeders.  They  make  larger 
holes,  and  eat  more  skin ;  hence  there  is  greater  probability  that  they  will 
take  in  poison  and  succumb  under  its  action. 

But  even  with  our  most  careful  spraying  in  a  commercial  way,  where 
Paris  green  is  generally  used  at  the  rate  of  four  ounces  to  fifty  gallons, 
there  are  ample  opportunities  for  curculios  to  puncture  the  fruit  and  still 
escape  injury.  The  writer  has  examined  a  large  number  of  apples  taken 
from  trees  that  had  been  thoroughly  sprayed,  and  finds  that,  as  a  rule, 
many  particles  of  the  poison  can  be  detected  on  the  fruit  surface,  but  no 
fruit  has  been  seen  that  approached  being  completely  covered.  On  all 
there  are  many  areas  where  the  curculio  could  work  with  impunity. 
Very  young  fruits  catch  and  retain  more  particles  of  the  poison  than  do 
older  fruits.  This  is  because  of  the  pubescence.  As  the  fruit  grows,  this 
pubescence  is  shed,  and  the  poison  of  early  applications  largely  goes  with 
it.  In  later  applications,  some  particles  will  find  lodgment  immediately 
about  the  stem  or  in  the  basin  of  the  calyx,  at  which  points  the  pubes- 
cence is  more  tardily  cast  off,  but  proportionately  very  few  particles 
are  caught  and  retained  on  the  smooth  surface  of  the  fruit. 

SPRAYING   EXPERIMENTS   IN   1904. 

The  character  of  the  results  of  the  spraying  experiments  in  1903,  as 
detailed  in  the  preceding  pages,  made  repetition  of  the  work  under  differ- 
ent circumstances,  if  not  actually  essential,  at  least  desirable.  It  was 
determined  to  secure,  if  possible,  the  use  of  an  isolated  orchard,  of  such 
size  that  it  could  be  treated  entire.  This  plan  would  eliminate  any  pos- 
sible modification  of  results  from  ingress  to  the  plats  of  new  insects  from 
surrounding  orchards.  After  examination  of  several  orchards,  which 
from  size  or  situation  were  deemed  unsuitable  to  our  purpose,  selection 
was  finally  made  of  the  orchard  of  Mr.  John  Sawdon,  situated  two  miles 
south  of  Griggsville  and  about  eighteen  miles  distant  from  the  orchards 
used  in  1903.  This  orchard  is  a  little  over  five  acres  in  extent,  and  was 
planted  twelve  years  ago  with  260  trees;  ten  rows  of  twenty-six  trees  each. 
The  four  west  rows  are  Ben  Davis,  the  two  central  rows  Wealthy,  and  the 
four  east  rows  Milam.  It  is  back  some  distance  from  the  highway,  and 
the  nearest  bearing  orchard  is  nearly  a  half  mile  distant.  The  surface  is 
somewhat  uneven  and  broken  by  two  gullies  which  cross  it.  The  orchard 


542 


BULLETIN    No.  98. 


[February, 


had  never  been  sprayed,  and  has  not  been  cultivated  for  several  years. 
It  is  now  in  grass,  and  a  crop  of  timothy  was  removed  last  year. 

Mr.  Sawdon  kindly  placed  the  orchard  in  charge  of  the  department  for 
such  experiments  as  might  be  decided  upon,  and  work  was  commenced  in 
April.  Mr.  James  R.  Shinn,  who  had  charge  of  the  work  at  Barry  during 
most  of  the  season  of  1903,  was  placed  in  immediate  charge  of  the  work 
here,  and  remained  with  it  until  the  close  of  the  season.  Many  of  the 
experiments  undertaken  involved  details  requiring  infinite  patience  and 
close  attention.  Their  successful  termination  is  entirely  due  to  the  un- 
tiring persistence  of  Mr.  Shinn. 

The  Ben  Davis  trees,  occupying  the  four  west  rows,  were  chosen  for 
curculio  experiments,  because  they  supplied  in  one  body  the  desired  num- 
ber of  trees,  and  would  be  comparable  with  the  trees  of  the  same  variety 
treated  last  season.  The  rest  of  the  orchard  was  taken  in  hand  for  an  ex- 
periment testing  the  relative  merits  of  liquid  spray  as  compared  with  dust 
spray.  Most  of  the  trees  were  sprayed  as  often  and  as  late  in  the  season 
as  were  the  trees  in  the  curculio  experiment,  and  we  have  no  evidence  that 
their  presence  in  any  way  modified  the  results  of  the  work  against  curculio. 

The  trees  chosen  were  divided  into  six  plats,  as  shown  in  the  accom- 
panying diagram,  and  the  schedule  of  applications  was  the  same  as  used  at 
Barry  in  1903.  The  dates  of  application,  however,  were  different,  owing 
to  the  fact  that  the  season  was  two  weeks  later  than  in  1903. 

THE   WINDFALLS. 

The  first  gathering  of  apples  was  commenced  June  29th  and  finished 
July  12th.  Examination  of  these  small  apples  required  infinite  care 
and  patience  in  order  to  determine  and  correctly  record  the  character 
and  number  of  punctures  made.  It  was  necessary  to  do  the  work  under 
a  lens.  This  consumed  time,  and,  as  fruit  was  picked  up  only  as  fast  as 
the  examination  could  be  made,  two  weeks  passed  before  the  first  picking 
was  completed.  Subsequent  collections  were  made  in  much  less  time, 
because  as  the  fruit  grew  larger,  examination  could  be  more  quickly  made. 
Fallen  fruit  was  gathered  nine  times;  the  last  time  October  14th,  just 
before  commencing  the  final  picking  of  fruit  from  the  trees.  The  fol- 
lowing tabulation  gives  the  number  of  fallen  apples  by  plats,  and  shows 
the  extent  to  which  they  were  punctured. 


^ 

PLUM  CURCULIO. 

APPLE  CURCULIO. 

£ 

u 

'on 

6  1 

OJ   0 

£% 

No.  of 

Not 

Crescent 

Feeding 

Egg 

Feeding 

£* 

R| 

apples. 

punctures. 

punctures. 

punctures. 

punctures. 

tured. 

fe 

No. 

Fruits. 

No. 

Fruits. 

No. 

Fruits. 

No. 

Fruits. 

1 

13 

3 

5056 

5599 

2612 

9366 

2531 

306 

228 

1395 

506 

1323 

2 

14 

10 

4281 

3164 

1696 

4334 

1572 

289 

237 

1400 

387 

1634 

3 

13 

16 

2467 

983 

632 

1577 

776 

77 

66 

639 

221 

1239 

4 

15 

8 

2831 

1663 

956 

2393 

992 

141 

111 

885 

289 

1177 

5 

13 

7 

3255 

1826 

1073 

3405 

1267 

181 

152 

1258 

431 

1197 

6 

12 

7 

6066 

3458 

2057 

4124 

1868 

183 

151 

1451 

474 

2663 

Totals  

23956 

16693 

9026 

25199 

9006 

1177 

945 

7028 

2308 

9233 

1905. 


THE   CURCULIO   AND  THE  APPLE. 


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ORCHARD  or  JOHM  5AWDOH    GRIGCSVILLE   ILL, 


PLATE  20. 


544  BULLETIN    No.  98.  [February, 

The  tabulation  shows  a  total  of  23,956  windfalls,  which  number 
represents  32.85  percent  of  all  the  fruits  borne  on  the  plats.  It  will  be 
noted  that  plat  1,  receiving  three  applications  of  spray,  shows  a  con- 
siderably greater  percentage  of  punctured  fruits  than  do  the  other  plats, 
and  that  plat  3,  which  was  sprayed  sixteen  times,  shows  the  smallest 
percentage  of  punctured  apples.  It  is  also  apparent  that,  comparing  the 
two  species  of  curculio,  the  plum  curculio  made  much  the  greater  number 
of  punctures. 

Of  the  total  number  of  windfalls,  9,026,  or  37.67  percent  bore  crescent 
punctures.  Probably  not  all  of  these  fruits  fell  because  of  these  punc- 
tures, but  assuming  that  they  did,  there  remain  14,930  apples,  or  62.33 
percent  that  fell  from  causes  other  than  puncture  by  curculio.  The 
fall  of  a  large  part  of  these  apples  was  due  to  an  early  development  of 
scab  that  did  not  yield  readily  to  the  early  applications  of  Bordeaux 
mixture.  Some  fell  as  a  result  of  codling  moth  injury,  and  some  were 
brought  down  by  heavy  winds.  The  9,026  apples  bore  16,693  crescents, 
nearly  all  of  which  may  be  assumed  to  have  been  accompanied  by  eggs, 
from  a  large  proportion  of  which  larvae  could  develop.  Destruction  of 
this  fallen  fruit  would,  therefore,  destroy  many  larvae  and  thus  mate- 
rially aid  in  holding  the  insects  in  check.  In  this  connection  it  is  in- 
structive to  notice  the  distribution  of  windfalls  throughout  the  season. 
Our  23,956  windfall  apples  were  gathered  as  follows: 

1st  Picking  June    29  -  July    12 12837  or  53 . 59% 

2d  "  July     28  -  Aug.     1 1329  or    5.55% 

3d  "  Aug.       9        528  or    2.20% 

4th  "  Aug.     24  -             26 2338  or    9 . 76% 

5th  "  Sept.      1-               2 606  or    2.53% 

6th  "  "       13-             15 1005  or    4.20% 

7th  "  "       20  -             22 1243  or    5. 19% 

8th  "  "       28-             29 1156  or    4.82% 

9th  "  Oct.      14 2914  or  12. 16% 

The  intervals  are  not  regular,  but  in  a  general  way  the  figures  indi- 
cate the  distribution  over  the  season.  The  important  fact  is  that  more 
than  half  of  the  total  number  was  gathered  at  the  first  picking.  Of  the 
9,026  apples  bearing  crescents,  5,321,  or  58.95  percent,  were  included 
in  the  first  picking,  and  these  apples  carried  9,435,  or  56.52  percent,  of 
the  total  number  of  crescents.  Apples  gathered  at  the.  first  picking 
were  of  small  size,  mostly  very  small,  ranging  from  less  than  one-fourth 
inch  to  one  inch  in  diameter,  with  the  majority  in  the  smaller  sizes.  In 
gathering,  special  effort  was  made  to  get  everything  that  had  the  sem- 
blance of  an  apple.  The  ground  under  each  tree  was  gone  over  several 
times  until  no  more  could  be  found.  We  have  learned  that  no  apple  is 
too  small  to  be  punctured  by  the  curculio,  therefore  no  apple  is  too  small 
to  be  included  in  our  record. 

The  recommendation  that  fallen  fruit  be  destroyed  commonly  con- 


1905.]  THE   CUKCULIO   AND  THE  APPLE.  545 

veys  no  idea  of  these  first  fallen  apples.  The  mind  turns  to  the  tangible 
fruit  of  midsummer  and  fall,  and  where  the  recommendation  is  followed, 
the  small  apples  that  fall  in  early  summer  are  entirely  ignored.  These 
same  small  apples  are,  however,  an  important  factor,  and  should  be 
considered  in  any  systematic  attempt  to  control  the  ravages  of  the  plum 
curculio.  At  the  beginning  of  this  investigation,  the  development  of  larvae 
in  very  small  apples  was  looked  upon  as  doubtful.  It  did  not  seem  pos- 
sible for  an  apple  one-fourth  inch  or  less  in  diameter  to  supply  nourish- 
ment enough  to  bring  a  larva  to  full  maturity,  but  it  has  been  learned 
that  larvae  can  and  do  develop  in  just  such  apples.  Several  attempts 
were  made  to  ascertain  the  number  of  larvae  that  would  emerge,  and  the 
number  of  beetles  that  would  develop  from  known  numbers  of  these 
small  apples.  Results  from  these  efforts  were  seriously  disturbed  by 
the  depredations  of  ants  that  carried  off  the  larvae  as  they  emerged,  so 
that  in  no  case  did  we  secure  an  accurate  record.  The  results  in  the  two 
trials  that  were  least  interfered  with  by  ants  are  as  follows: 

In  one  case  1,576  small  apples  picked  up  under  one  tree  on  June 
10th  were  placed  on  earth  in  a  box  which  was  partially  sunk  in  the  ground 
and  then  covered  with  cheesecloth  held  firmly  in  place  by  tacks.  This 
lot  of  apples  is  shown  in  Plate  21.  At  the  proper  time  daily  examinations 
were  commenced  and  kept  up  as  long  as  beetles  continued  to  emerge. 
From  this  box  were  taken  222  plum  curculips  and  64  apple  curculios. 
Ants  did  not  infest  this  box  so  much  as  they  did  some  others,  but  there 
is  no  doubt  that  they  destroyed  some  larvae. 

In  another  box  similarly  situated  were  placed  2,535  small  apples 
picked  up  on  the  same  date.  From  this  we  took  944  plum  curculios 
and  39  apple  curculios.  Our  test  of  egg-laying  capacity  given  in  detail 
in  another  place  began  May  23d.  For  some  time  the  apples  supplied 
each  day  were  of  necessity  very  small,  but  eggs  were  deposited  in  them 
as'  freely  and  larvae  developed  as  well  as  in  the  larger  apples  used  later 
in  the  season.  There  is  no  doubt  that  plum  curculio  larvae  do  develop 
in  very  small  apples,  and  it  follows  that  these  apples  should  be  considered 
in  any  plan  for  repression.  To  gather  them  would  be  impracticable, 
but  if  clean  culture  is  practiced  they  and  the  larvae  they  contain  could 
be  largely  destroyed  by  use  of  the  disk  harrow  or  some  other  tool  that 
would  chop  them  up  or  bury  them.  If  the  ground  is  clean  and  the  or- 
chard sufficiently  open,  so  that  the  sun  can  shine  upon  the  apples  as  they 
lie  on  the  ground,  nothing  further  is  necessary,  because  direct  sunlight 
upon  the  apples  will  kill  the  contained  larvae. 

THE    PICKED   FRUIT. 

The  final  picking  of  fruit  from  the  trees  was  commenced  on  October 
14th  and  finished  on  October  20th.  Following  the  same  plan  used  with 
windfalls,  each  apple  was  examined,  and  record  made  of  the  number  and 


546 


BULLETIN    No.  98. 


[February, 


character  of  punctures  found.  A  force  of  eight  men  was  necessary  for 
this  work.  Three  examined  apples  and  called  the  punctures  to  three 
others  who  made  the  record  on  previously  prepared  forms.  These  forms 
were  made  for  individual  trees,  and  the  tables  were  moved  from  tree  to 
tree  as  the  work  advanced.  Two  men  picked  and  kept  the  tables  sup- 
plied with  apples.  Plate  22.  The  punctures  found  were  separated, 


«rx*  '••FT! 


••  .«     - 


*      v,      >    "rtr- 


PLATE  21.      Box  CONTAINING  1,576  SMALL  APPLES. 

according  to  purpose  and  the  insect  making  them,  into  four  classes  as 
follows : 

(  Crescents,  usually  accompanying  oviposition. 

Plum  Curcuho < ._     ,. 

(  r  eedmg  punctures. 

(  Eeg  punctures,  made  for  oviposition. 

Apple  Curcuho <  ™    j. 

(  Feeding  punctures. 

The  number  of  apples  picked  and  recorded  was  48,966,  or  67.55  per- 
cent of  all  fruits  borne  by  the  trees.  The  number  and  the  percent  punc- 
tured, and  the  number  and  percent  free  from  puncture  is  shown,  by  plats, 
in  the  following  tabulation. 


1905. 


THE   CURCULIO   AND   THE   APPLE. 


547 


548 


BULLETIN    No.  98. 


[February, 


RECORD  OF  PICKED  APPLES. 


No.  of 
plat. 

No.  of 
Trees. 

Times 
sprayed. 

Punctured. 

Not  punctured. 

Number. 

Percent. 

Number. 

Percent. 

1 
2 
3 
4 
5 
6 

13 
14 
13 
15 
13 
12 

3 
10 
16 

8 

7 

7 

3884 
5284 
2890 
5412 
4263 
3907 

75.73 
52.47 
34.43 
54.65 
51.14 
54.79 

1245 
4787 
5504 
4492 
4074 
3224 

24.27 
47.53 
65.57 
.    45.35 

48.86 
45.21 

Totals  .  . 

25640 

52.36 

23326 

47.64 

By  a  simple  computation  based  upon  the  percentage  of  fruit  liable 
to  puncture,  as  shown  by  the  check  plat,  it  is  found  that  the  percentages 
of  fruit  on  the  different  plats  saved  from  puncture  by  the  treatment 
applied  are  as  follows: 

Plat  2  shows  gain  over  the  check  plat  of  30.71% 
"     3     "  "  "  "         "        54.53% 

"     4     "  "  "  "         "        27.83% 

"     5     "  "  "  "         "        32.47% 

"     6     "  "  "  "         "        27.65% 

These  percentages  show,  in  close  approximation,  the"  relative  efficiency 
of  the  treatment  applied  to  different  plats. 

Of  the  23,956  windfalls,  14,723,  or  61.46  percent,  were  punctured, 
while  9,233,  or  38.54  percent,  were  free  from  puncture.  These  figures 
show  that  the  windfalls  were  punctured  to  a  somewhat  greater  extent 
than  were  the  picked  fruits.  Under  perfectly  natural  conditions,  how- 
ever, it  is  believed  the  picked  fruits  would  show  a  greater  aggregate 
number  of  punctures  than  the  windfalls.  It  will  be  understood  that 
the  majority  of  punctures  for  oviposition  are  made  comparatively  early 
in  the  season,  while  feeding  punctures,  more  particularly  those  made  by 
the  plum  curculio,  multiply  most  rapidly  late  in  the  season.  Fallen  apples 
over  the  whole  orchard  were  gathered,  and  no  beetles  developing  from 
them  were  allowed  to  return  to  the  trees.  This  reduction  of  the  new  crop 
of  beetles  without  doubt  greatly  diminished  the  number  of  late  feeding 
punctures  which  are  the  source  of  greatest  injury  to  the  apple  crop. 

The  punctures  found  on  the  picked  apples  are  classified  in  tabular 
form  below: 


"r? 

01  -a 

PLUM  CURCULIO. 

APPLE  CURCDLIO. 

A 

a  >> 

No.  of 

Crescent 

Feeding 

Egg 

Feeding 

Not 

Z*3 

S& 

apples. 

punctures. 

punctures. 

punctures. 

punctures. 

tured. 

fc 

No. 

Fruits 

No. 

Fruits. 

*  No. 

Fruits. 

No. 

Fruits. 

1 

13 

3 

5129 

3611 

2070 

11090 

3200 

202 

168 

2493 

722 

1245 

2 

14 

10 

10071 

3039 

2079 

9034 

3621 

339 

275 

3581 

1020 

4787 

3 

13 

16 

8394 

1248 

975 

3506 

1721 

154 

130 

1899 

591 

5504 

4 

15 

8 

9904 

1477 

1187 

10053 

4252 

218 

186 

2123 

745 

4492 

5 

13 

7 

8337 

1125 

938 

6815 

2996 

272 

241 

3156 

1006 

4074 

6 

12 

7 

7131 

937 

759 

8045 

3171 

173 

154 

2137 

725 

3224 

Totals  

48966 

11437 

8008 

48543 

18961 

1358 

1154 

15389 

4809 

23326 

1905.] 


THE   CURCULIO   AND  THE  APPLE. 


549 


It  will  be  seen  that  the  number  of  punctures  is  large,  aggregating 
many  more  than  are  shown  on  the  windfalls,  but  the  number  of  fruits  is 
more  than  double  and  the  percentage  punctured  somewhat  less  than  for 
windfalls.  Computing  the  number  of  punctures  for  each  apple  punctured, 
it  is  found  that  crescent  punctures  average  1.85  for  each  windfall  and  1.42 
for  each  picked  apple.  Feeding  punctures  average  2.8  for  each  windfall  and 
2.56  for  each  picked  apple.  Apple  curculio  egg  punctures  show  the  same 
relation,  an  average  of  1.24  for  each  windfall  and  1.17  for  each  picked  fruit. 
With  apple  curculio  feeding  punctures  the  balance  is  the  other  way,  wind- 
falls have  an  average  of  3.04  while  picked  apples  average  3.20  punctures 
for  each  apple  punctured.  Some  apple  curculios  of  the  new  generation 
emerged  from  apples  on  the  trees,  and  probably  did  some  feeding  on  fruit 
before  going  into  retirement.  This  may  account  for  the  greater  number 
of  feeding  punctures  on  picked  fruit. 

Bringing  all  the  apples  together,  and  arranging  the  number  and 
percent  of  punctured  for  comparison  with  the  fruit  not  punctured,  we 
have  the  following: 


No.  of 
plat. 

No.  of 

trees. 

Times 
sprayed. 

Punctured. 

Not  punctured. 

Total 
apples. 

Number 

Percent. 

Number. 

Percent. 

1 
2 

3 
4 
5 
6 

13 
14 
13 
15 
13 
12 

3 

10 
16 

8 

7 
7 

7617 
7931 
4118 
7066 
6321 
7310 

74.79 
55.26 
37.92 
55.48 
54.53 
55.39 

2568 
6421 
6743 
5669 
5271 
5887 

25.21 
44.74 
62.08 
44.52 
45.47 
44.61 

10185 
14352 
10861 
12735 
11592 
13197 

Totals  .  . 

40363 

55.35 

32559 

44.65 

72922 

In  this  consideration  of  all  fruits,  both  picked  and  windfalls,  the  check 
plat  which  received  only  the  three  early  applications  shows  74.79  percent 
of  the  fruit  punctured. 

Plats  2,  4,  5,  and  6  show  striking  uniformity  in  the  percentages  of 
fruit  punctured,  and  plat  3  shows  a  marked  gain  over  all  other  plats  in 
the  amount  of  fruit  free  from  punctures.  This  plat  received  thirteen 
applications  of  spray  after  the  first  three,  making  a  total  of  sixteen, 
and  the  relatively  small  percent  (37.92)  of  punctured  fruit  is  ascribed 
to  these  numerous  applications,  but  how  much  of  this  freedom  from 
puncture  is  due  to  an  increased  number  of  insects  poisoned  and  how  much 
to  the  repellent  action  of  the  frequent  applications,  is  not  determined. 
From  the  record  of  the  check  plat,  which  shows  74.79  percent  of  the  fruit 
punctured,  the  percent  of  gain  for  each  of  the  other  plats  is  computed  as 
follows : 

Plat  2  with  10  applications  shows  gain  over  the  check  of  26. 11% 
"     3     "     16          "  "         "  "  "         49.29% 

"     4     "       8          "  "         "  "  "         25.83% 

"     5     "       7  "  "  "         27.08% 

"     6     "       7  "         "  "  "         25.93% 


550  BULLETIN    No.  98.  [February, 

In  conducting  the  experiments  in  that  portion  of  this  orchard  outside 
the  curculio  plats,  certain  check  trees  that  received  no  treatment  what- 
ever were  maintained.  Record  was  made  of  all  defects  in  fruits  borne 
by  these  trees,  and  we  find  that  88.21  percent  of  the  fruit  was  punctured 
by  curculio.  Comparing  these  trees  with  our  curculio  check  plat,  we  find 
that  the  three  early  applications  of  spray  effected  a  saving  of  15.21  percent 
in  amount  of  fruit  punctured.  Computing  in  like^manner  from  the  trees 
receiving  no  spray,  our  plat  No.  3,  which  received  sixteen  applications, 
shows  a  gain  of  57.01  percent. 

It  appears  from  the  foregoing  that  when  all  fruits  are  considered,  three 
applications  of  spray  may  effect  a  saving  of  15.21  percent  of  fruit  liable  to 
puncture,  and  that  sixteen  applications  may  effect  a  saving  of  57.01  per- 
cent. If  we  considered  picked  fruit  only,  the  range  of  benefit  lies  between 
14.14  percent  and  60.96  percent,  but  the  larger  number  of  applications 
cannot  be  commended  for  commercial  orchards  because  of  the  attending 
expense.  Careful  orchardmen  would  consider  four  or  even  five  applica- 
tions as  possible,  but  beyond  that  most  of  them  would  not  consent  to  go. 
This  suggested  possible  number  of  applications  would  presumably  effect  a 
saving  of  from  20  to  40  percent  of  fruit  liable  to  puncture,  provided  the 
conditions  were  as  favorable  as  those  surrounding  our  work  during  1904. 

Plate  23,  from  a  photograph  of  tree  No.  54  of  plat  4,  shows  a  fair 
average  of  the  trees  treated  in  this  orchard.  In  Plate  24  the  fruit  from 
this  tree  is  shown : 

First,  as  separated  into  punctured  and  not  punctured. 

5  bushels  not  punctured 637  apples 

5  bushels  punctured 645  apples 

Total  apples    1,282 

Second,  as  separated  into  market  grades. 

5  bushels  No.  1 564  apples 

4^  bushels  No.  2 635  apples 

Yi  bushel  culls    83  apples 


Total  apples    1,282 

The  number  of  apples  and  the  proportion  punctured  varies  greatly 

with  the  trees  on  different  plats. 

Under  the  conditions  prevailing  in  1903,  no  benefit  from  spraying 

could  be  predicted.     We  may  compare  the  two  seasons,  in  parallel,  as 

follows : 


1903. 

1904. 

Weather  conditions  in 
spring. 

Crop.                    / 
Location. 

Curculios. 

Bad.     Cold  rains  and 
frost. 

Very  few  apples. 
Small  blocks  in  large 
orchards. 
Excessively  abundant. 

Season  somewhat  late,  but 
in  general  favorable  to 
fruit. 
Good  crop  of  fruit. 
Small  isolated  orchard. 

Comparatively  few. 

1905.] 


THE"  CUKCULIO   AND  THE  APPLE. 


551 


PLATE  23.      TREE  No.  54  OF  PLAT  4. 


552 


BULLETIN    No.  98. 


[February, 


1905.]  THE   CTJRCULIO  AND  THE  APPLE.  553 

Abundance  of  curculios  is  the  most  important  factor  influencing  re- 
sults, and  in  this  respect  the  two  seasons  are  not  comparable.  Had  the 
curculios  been  as  abundant  in  1904  as  in  1903,  it  is  questionable  if  the 
work  of  spraying,  which  was  identical  with  the  work  done  in  1903,  would 
have  shown  any  better  results  than  were  obtained  the  previous  year. 

To  sum  up  the  whole  matter  of  spraying  for  curculio,  from  the  stand- 
point of  results  obtained  during  the  two  seasons  of  1903  and  1904,  it 
seems  possible,  under  favorable  conditions,  and  with  a  reasonable  number 
of  applications,  to  control  curculios  to  the  extent  of  from  20  to  40  percent 
of  the  possible  injury.  There  is  benefit  to  be  derived  from  spraying,  but 
not  that  degree  of  benefit  which  would  warrant  commendation  of  spraying 
as  the  one  great  panacea  for  the  injury  done  by  curculios.  For  satisfac- 
tory results,  spraying  must  be  supplemented  by  attack  from  other  direc- 
tions. Attention  to  fallen  fruit  has  been  already  commented  upon,  and 
is  a  means  of  attack  worthy  of  consideration. 

The  depth  of  pupation,  and  the  period  during  which  pupae  are  in  the 
ground,  are  matters  that  have  been  discussed  on  preceding  pages.  It  has 
been  shown  that  the  major  portion  of  the  new  generation  of  plum  curculio 
is  in  the  earth,  within  two  inches  of  the  surface,  for  a  period  of  thirty  days 
from  July  10th.  The  common-sense  method  of  attack  that  is  at  once 
suggested  is  cultiv  tion. 

CULTIVATION  AS   A    MEANS   OF   REPRESSION. 

Superficial  tillage  of  the  surface  soil  can  be  commended  as  an  effective 
method  of  attacking  curculio.  This  tillage  should  be  carried  on  continu- 
ously or  at  frequent  intervals  for  a  period  of  from  thirty  to  forty  days,  dur- 
ing which  the  great  bulk  of  the  new  crop  of  plum  curculios  is  in  the  ground. 
The  object  of  tillage  is  to  turn  the  pupse  out,  kill  some  in  the  process,  and 
expose  the  rest  to  the  elements  and  to  birds  and  insects  that  prey  upon 
them.  Pupae  of  the  plum  curculio  are  extremely  delicate,  and  they  are 
incapable  of  moving  about.  In  digging  for  pupse  it  was  observed  that 
admission  of  air  to  the  burrow  invariably  caused  immediate  distress;  the 
pupse  would  squirm  and  wriggle  as  if  in  pain.  Actual  triaf  proved  that 
sunlight  was  quickly  fatal,  and  that  exposure  on  the  surface  in  the  shade, 
on  a  warm  day,  would  kill  in  a  few  hours.  It  was  also  demonstrated  that 
birds,  ants,  and  other  insects  devour  exposed  pupae  greedily.  In  view  of 
the  results  obtained  in  this  work  with  pupse,  the  definite  statement  is 
warranted  that  cultivation  with  disc  or  harrow  will,  in  great  measure, 
prevent  the  maturation  of  these  insects  and  at  less  cost  than  by  any  other 
means. 

For  those  orchards  in  which  cultivation  has  been  practiced,  the  treat- 
ment suggested  would  not  be  a  serious  burden,  simply  a  prolongation  or 
repetition  of  work  easily  and  rapidly  done,  but  'for  orchards  that  have  not 
had  the^ground  disturbed  for  several  years,  and  are  either  heavily  sodded 


554  BULLETIN    No.  98.  [February, 

or  thickly  grown  up  with  weeds,  the  cultivation  recommended  is  not  so 
simple  a  matter.  However,  it  is  the  grassy  and  weedy  orchards  that  need 
the  treatment  most,  because  it  is  in  such  orchards  that  the  curculio  is 
doing  the  most  damage.  Observations  made  in  a  considerable  number 
of  orchards  in  various  parts  of  the  state  make  it  plain  that  uncultivated 
orchards  suffer  greatest  injury  from  curculio,  and  the  reason  seems 
equally  plain.  Grass  and  weeds  offer  hiding-places  where  curculios  in  the 
beetle  stage  are  safe  from  most  of  their  natural  enemies,  where  fallen 
apples  may  slowly  decay  and  nourish  larvaB  to  full  development,  and 
where  pupae  may  rest  securely  until  the  transformations  are  complete  and 
the  perfect  beetle  ready  to  emerge.  The  conditions  are  ideal  for  bringing 
to  adult  form  the  largest  possible  percentage  of  the  insects.  They  have 
things  their  own  way,  are  correspondingly  prolific,  and  there  follows  a 
corresponding  amount  of  injury.  To  do  away  with  these  conditions,  so 
favorable  to  insect  development,  to  eradicate  the  grass  and  weeds,  to 
clean,  pulverize,  and  smooth  the  surface  soil,  and  thus  bring  conditions 
least  favorable  to  curculios,  is  a  task  demanding  thoughtful  planning  and 
skillful  execution.  It  means  the  outlay  of  time,  labor,  and  money,  pro- 
portionate to  the  size  of  the  orchard  and  the  length  of  time  it  has  been 
neglected;  and  greater  or  less,  according  as  the  weather  conditions  are 
favorable  or  unfavorable,  passage  between  trees  unobstructed  by  drooping 
branches,  and  the  ground  free  from  dead  brush  and  other  rubbish  too 
heavy  for  ordinary  tools  to  contend  with.  In  some  orchards  a  severe 
pruning  of  lower  limbs  would  be  imperative  before  any  attempt  could  be 
made  at  cultivation.  Neglect  of  pruning  usually  accompanies  neglect  of 
cultivation,  and  too  frequently  the  orchard  becomes  impassable  for  teams, 
necessitating  considerable  expenditure  preparatory  to  the  cultivation  pro- 
posed. When  orchards  present  conditions  such  as  here  referred  to, 
owners  are  inclined  to  hesitate  and  count  the  cost.  The  dilemma  pre- 
sented is  not  attractive,  for  intelligent  consideration  is  quite  certain 
to  resolve  the  question  into  a  choice  between  grubbing  out  the  orchard 
and  placing  it,  at  whatever  cost,  in  condition  again  to  give  profitable  re- 
turns. There  are  many  orchards  which  present  this  problem,  or  would 
present  it  if  judged  according  to  actual  existing  conditions,  and  the  choice 
of  procedure  is  not  easy.  No  fixed  rule  can  determine  how  bad  orchards 
must  be  to  place  them  beyond  possibility  of  renovation  with  reasonable 
expenditure,  because  no  two  orchards  are  alike,  and  conditions  are  various. 
The  best  course  to  pursue  must  be  determined  in  each  individual  case  by 
careful  study.  Then,  if  such  study  be  supported  by  good  judgment  and 
knowledge  of  horticultural  principles,  it  will  be  possible  to  bring  rpany 
neglected  and  unprofitable  orchards  to  a  state  of  productiveness  that  will 
amply  repay  the  effort  and  the  cost. 

Those  who  put  in  practice  the  suggested  means  of  holding  the  cur- 
culio in  check  need  apprehend  no  serious  trouble  from  these  insects  in 


1905.]  THE   CURCULIO   AND  THE  APPLE.  555 

ordinary  years  unless  injury  results  through  invasion  from  neighboring 
orchards  that  are  neglected  and  that  serve  as  harbors  and  breeding  places. 

Years  of  excessive  abundance  of  curculios  will  undoubtedly  recur, 
but  orchards  that  are  pruned,  cultivated,  and  sprayed  are  not  likely  to 
suffer  serious  injury.  It  is  the  neglected  orchards,  those  affording  ideal 
conditions  for  insect  development,  that  will  suffer  most  in  these  years  of 
abundant  insects. 

Curculios,  like  many  other  insects,  appear  to  run  in  cycles.  Years  of 
great  abundance  are,  through  natural  causes,  followed  by  years  of  com- 
parative scarcity. 

Persistent  application  of  artificial  means  of  repression  will  reduce 
injury  to  its  lowest  point  in  years  of  scarcity,  make  the  recurrence  of 
maximum  injury  less  frequent,  and  greatly  mitigate  the  injury  in  years 
when  insects  are  most  abundant. 

It  should  be  remembered  that  curculios  are  not  the  only  orchard  pests, 
and  that  means  of  repression  directed  against  these  insects  are  equally 
effective  in  controlling  other  insects  which  are  more  or  less  injurious 
every  year. 

Spraying  is  an  essential  practice  for  the  control  of  apple  scab  and  other 
fungous  diseases.  Arsenical  poisons  applied  with  the  Bordeaux  mixture 
add  little  to  the  expense  and  are  even  more  effective  in  checking  the  rav- 
ages of  codling  moth,  canker  worm,  and  other  leaf -eating  insects  than 
they  are  in  destroying  curculios.  The  practice  of  destroying  fallen  fruit 
commended  as  a  means  of  attacking  curculio  is  equally  effective  against 
codling  moth  and  at  the  same  time  aids  in  preventing  the  spread  of  some 
destructive  fungi. 

Cultivation  is  an  effective  means  for  destroying  plum  curculio  pupae 
and  for  promoting  conditions  generally  unfavorable  to  insects,  but  the 
benefits  of  cultivation  do  not  end  here.  The  physical  condition  of  the  soil 
is  improved  and  plant  food  rendered  available.  Growth  of  both  tree  and 
fruit  is  stimulated  and  the  increased  vigor  insures  greater  resistance  to 
the  ravages  of  insects  and  diseases.  In  view  of  the  wide-reaching  effects 
of  the  means  commended  for  the  destruction  of  curculio,  the  cost  attending 
their  application  is  not  chargeable  to  curculio  alone.  To  fight  curculio  is 
virtually  to  attack  all  orchard  pests  and  to  make  right  any  conditions 
not  favorable  to  the  growth  and  productiveness  of  orchard  trees. 


556  BULLETIN    No.  98.  [February, 

CONCLUSIONS. 

The  primary  cause  of  serious  injury  to  apples  by  curculios  can  in  the 
majority  of  cases  be  traced  to  conditions  prevailing  in  the  orchards. 
Neglect  of  the  four  cardinal  principles  of  good  orchard  management, 
namely,  pruning,  cultivation,  spraying,  and  fertilizing,  engenders  con- 
ditions favorable  to  the  multiplication  of  curculios  and  also  of  other  pests. 
Weeds  and  grass  grow  unrestrained,  tree  tops  become  dense,  and  the  con- 
sequent heavy  foliage  affords  deep  shade.  The  insects  are  undisturbed, 
they  find  protection  against  natural  enemies,  and  their  processess  of 
development  go  on  unchecked.  As  the  insects  multiply  the  injury  in- 
creases until  crops  are  utterly  ruined. 

The  factor  of  location  has  an  influence  and  will  account  for  heavy 
losses  from  curculio  injury  that  sometimes  occur  even  in  orchards  that 
are  given  every  attention.  If  cultivated  orchards  are  in  close  proximity 
to  badly  neglected  orchards,  or  to  bodies  of  timber  in  which  the  native 
food  plants,  hawthorn,  wild  crab,  and  wild  plum,  are  abundant,  such  or- 
chards may  be  invaded  by  curculios  and  the  fruit  greatly  injured.  Such 
situations  are  unfortunate  and  usually  cannot  be  changed  or  improved. 

It  seems  possible  to  attack  the  curculio  in  three  different  ways. 

First — By  spraying  with  arsenical  poisons.  This  method  aims  at 
the  destruction  of  the  adult  or  beetle  stage  of  the  insect  only.  This  method 
as  used  in  our  experiments  at  Barry  in  1903  proved  ineffective  as  is  shown 
by  the  tabulations  on  page  538.  Reasons  for  these  results  are  found  in 
three  factors  or  conditions : 

A — Small  amount  of  fruit  borne  by  the  trees. 

B — Location  of  the  treated  plats  in  the  midst  of  large  orchards. 

C — Excessive  abundance  of  the  insects. 

The  same  treatment  applied  in  1904  in  a  small  isolated  orchard  which 
bore  a  good  crop  of  fruit  and  with  the  insects  much  less  abundant  resulted 
in  saving  from  27.65  percent  to  54.53  percent  of  the  picked  fruit  liable 
to  puncture.  The  percentage  of  gain  varied  between  the  limits  given, 
according  to  the  number  of  times  the  trees  were  sprayed.  But  sixteen 
applications  were  required  to  attain  the  higher  percentage  and  this  in- 
volves too  great  an  expense  to  warrant  commending  such  procedure. 

Under  favorable  conditions  from  twenty  to  forty  percent  of  the  fruit 
liable  to  puncture  may  be  saved  by  five  applications,  and  this  treatment 
is  regarded  as  profitable  and  practicable. 

Second— By  destruction  of  fallen  fruit.  This  method  of  attack  aims 
at  the  egg  and  larva  stages  of  the  insect.  All  fallen  fruit  must  be  taken 
into  account,  not  only  the  larger  fruits  that  fall  in  late  summer,  but  more 
-particularly  the  small  apples  that  fall  in  June  and  early  July.  The  early 
fallen  fruit  is  usually  ignored,  but  is  really  more  important  from  the  stand- 


1905.]  THE  CURCULIO  -AND  THE  APPLE.  557 

point  of  attack  on  curculio  than  the  late  fallen  fruit,  because  oviposition 
and  larval  development  is  at  its  highest  early  in  the  season.  Experiments 
made  during  this  investigation  demonstrate  conclusively  that  destruction 
of  the  small  apples  is  important.  Gathering  them  is  regarded  as  imprac- 
ticable because  of  small  size  and  great  numbers.  If  the  orchard  is  suffi- 
ciently open  and  the  ground  clean  so  that  the  sun  can  act  upon  the  apples 
the  desired  end  will  be  accomplished  because  repeated  trials  have  shown 
that  action  of  the  sun  will  kill  larvae  contained  in  fallen  apples.  If  shade 
under  trees  is  too  dense,  the  apples  could  be  raked  together  in  exposed 
spots  at  small  expense  and  no  doubt  many  of  them  would  be  destroyed 
during  the  cultivation  necessary  to  keep  the  ground  clean. 

Third — Cultivation.  This  method  of  attack  is  directed  against  the 
insect  in  the  ground  and  may  affect  the  three  stages,  larva,  pupa,  and 
beetle,  but  is  more  particularly  intended  to  destroy  pupae. 

The  experiments  given  have  demonstrated: 

First. — That  the  average  time  spent  by  the  insect  in  the  ground, 
based  on  the  records  for  1,264  individuals,  is  twenty-eight  days. 

Second. — That  the  period  during  which  curculios  were  in  the  ground 
was  for  the  season  of  1904,  143  days,  or  from  June  17th  to  November  7th. 

Third. — That  the  majority  of  the  new  crop  of  insects  are  in  the  ground 
during  July  and  August,  and  computing  from  the  record  of  1,700  larvae 
entering  the  ground,  a  period  of  thirty  days  from  July  10th  will  find 
87%  in  the  ground;  forty  days  from  the  same  date  will  affect  92%  and 
fifty- three  days  nearly  97%. 

Fourth. — That  depths  recorded  for  824  pupae  range  between  one- 
fourth  inch  and  three  and  one-half  inches.  At  depths  of  two  inches  and 
less  we  find  772,  or  93.69%  of  the  total  number,  and  at  depths  of  one  inch 
and  less  516,  or  62.62%. 

Fifth. — That  both  larvae  and  pupae  are  very  delicate  and  extremely 
sensitive  to  exposure  to  light  and  air. 

Sixth. — That  short  exposures  to  direct  sunlight  are  fatal  to  both  larvae 
and  pupae. 

Seventh. — That  ants  and  other  predaceous  insects,  as  well  as  birds, 
prey  upon  both  larvae  and  pupae. 

In  the  light  of  these  facts  superficial  tillage  for  a  period  of  thirty  or 
more  days  from  July  10th  is  commended  as  an  efficient  means  of  attack- 
ing plum  curculios. 

To  advocate  measures  against  curculios  is  in  effect  to  urge  the  main- 
tenance of  better  orchard  conditions.  The  state  of  orchard  culture  most 
favorable  to  the  production  of  profitable  crops  is  correspondingly  un- 
favorable to  the  development  of  insects  and  the  spread  of  fungous  diseases. 

Best  results  can  only  be  attained  through  intensive  culture  and  to 
aim  at  these  best  results  is  simply  to  apply  to  the  management  of  orchards 
that  same  business  sense  that  brings  success  in  other  commercial  ventures. 


INDEX. 

Ants,  destroy  larvae  and  pupae,  489. 

Apple  Curculio  (Anthonomus  quadrigibbus,  Say) : 

Appearance,  time  of,  516. 

Eggs,  deposited  during  day,  523;  number,  during  night,  523;  number  on  sur- 
face of  fruit,  523;  deposition  process,  516;  description,  516;  number,  522; 
time  required  to  hatch,  516. 

Egg-punctures,  number,  523,  549;  number  in  windfalls,  542;  number  in 
picked  fruit,  549;  number  in  neglected  fruit,  511;  number,  relative  in 
windfalls  and  picked  fruit,  549;  process  of  making,  516;  size  and  descrip- 
tion, 519;  without  eggs,  519,  522,  523. 

Feeding  habits,  512,  526,  540. 

Feeding  punctures,  effect  on  apples,  524;  number,  524,  549;  number  on 
neglected  fruit,  511;  number  during  day,  523;  number  during  night,  523; 
number  in  windfalls,  542;  number  in  picked  fruit,  549;  number,  major 
portion  made  by  males,  524;  number,  relative,  in  picked  fruit  and  windfalls, 
549;  size  and  description,  524. 

Food  plants,  514. 

Geographical  distribution,  514;  recorded  by  Le  Baron,  515. 

Habits,  515;  compared  with  those  of  Plum  Curculio,  528;  course  of  flight, 
528;  effect  of  light,  528;  egg-eating,  521;  nocturnal,  529. 

Hibernation,  526. 

Injurious  effects,  1,  542;  compared  with  those  of  Plum  Curculio,  528. 

Larva1,  description,  525;  feeding  habits,  525;  time  for  full  development,  526. 

Life  cycle,  established  by  Riley,  515. 

Mortality,  cause,  527. 

Nativity,  468. 

Oviposition,  description  of  process,  517;  duration  and  number  of  eggs  laid, 
experiments,  521-524;  effect  on  fruit,  519-520;  notes  on,  522;  Gillette  on, 
516;  period,  521. 

Paris  green,  effect,   540. 

Period  of  development,  526. 

Time  in  fruit,  526. 
Birds  destroy  larvae  and  pupae,  553. 
Brackett,  G.  C.,  experiments  with  London  purple,  532. 

Curculio,  factors  influencing  experiments  against,  552;  conditions  ideal  for  their 
development,  554;  investigation,  causes,  and  lines,  468;  periodic  in 
appearance,  555. 

Curculio  injury,  549;  amount  in  neglected  orchards,  467;  extent  in  Pike  County, 
468.  512;  greater  near  timber,  467,495:  location  of  orchards  affecting,  556; 
number  and  percent  of  crop  damaged,  538,  549;  number  and  percent 
of  picked  apples  damaged,  548;  number  and  percent  of  windfall  apples 
damaged,  542;  recorded  by  Walsh,  471;  small  apples  affected,  544. 
Drouth,  effect  on  transforming  plum  curculios,  491. 

Forbes,  S.  A.,  curculio  feeding  habits,  experiments,  497;  experiences  with  arseni- 
cals  for  curculio,  532. 

558 


INDEX.  559 

Gillette,  C.  P.,  first  to  record  process  of  oviposition  by  apple  curculio,  516. 

Investigations,  cause  and  lines,  468. 

Kennicott,  John  A.,  quoted,  471. 

Kenrick,  quoted,  470. 

Le  Baron,  quoted  on  distribution  and  food  habits  of  apple  curculio,  515. 

Litner,  quoted,  regarding  Plum  Curculio  in  spring,  496. 

Picked  apples,  number  and  percent,    538,    546;    records,  methods    of     securing, 

546;  number  not  injured  by  curculios.  538,  549. 
Plum  Curculio  (Conotrachelus  nenuphar,  Herbst) : 

Appearance,  time  in  spring,  473,  496;  newly  emerged,  time,  490. 

Crescents,  eggs  not  always  accompany,  502,  507,  508,  511;  egg-cavities  lacking, 
502;  egg-cavities,  position,  502;  notes  on,  512;  number    by  individual  in- 
sects, 508;  number  in  picked  apples,  549;  number  in  unsprayed  apples,  511: 
number  in  windfalls,  510,  542;  process    of    making,    500;   proportion  to 
.  feeding  punctures,  by  Titus,  511 ;  season  of  abundance,  510. 

Development,  in  apples  by  Webster,  512;  in  smalLapples,  475. 

Eggs,  crescents  not  always  accompany,  507,  508;  deposition,  process,  500; 
deposited  in  crescents,  502;  description,  474;  destruction  by  predatory 
insects,  475;  failure  to  hatch,  474;  number  in  windfalls,  504;  number  laid 
during  night,  508;  number  laid  during  day,  508;  number  per  day  and  sea- 
son for  individuals,  508;  number  per  day  and  season  for  individuals,  by 
Quaintance,  505;  period,  474. 

Egg-cavities,  appearance,  504;  crescents  not  always  accompany,  502;  eggs 
not  always  accompany.  502;  number  per  crescent,  502;  position  in  cres- 
cent, 502;  preparation,  process  described,  500;  size,  501. 

Feeding  habits,  473,  492,  493,  495,  510,  541;  experiments  on,  by  S.  A.  Forbes, 
497;  number  of  punctures  and  time  of  making,  508;  number  of  punctures 
abundant  in  unsprayed  apples,  511. 

Feeding  punctures,  number,  549;  number  and  time  of  making,  508;  num- 
ber in  windfalls,  542;  relative  number  in  picked  and  windfall  apples, 
549. 

Food  plants,  467,  469,  471. 

Geographical  distribution,  472. 

Habits-,  effect  of  darkness,  508;  effect  of  light,  528;  flying,  course,  528;  fruit 
infested,  468,  473;  in  spring,  495;  nocturnal,  528;  time  in  fruit,  473,  476; 
time  in  ground,  487,  557;  time  of  emergence  of  beetles,  491. 

Hibernation,  473,  494. 

Historical  note,  469. 

Injury,  comparison  with  apple  curculio,  528,  544;  notes,  467,  544;  notes  by 
Kenrick,  470;  notes  by  Kennicott,  471. 

Larvae,  behavior  after  leaving  fruit,  478;  course  in  fruit,  475;  description,  475, 
development  in  decayed  apples,  475;  development  not  reached  on  trees,  475; 
effect  of  exposure,  557;  effect  of  sunlight,  478,  487;  emergence,  476; 
mortality  and  cause,  479;  number  developing  in  windfalls,  512;  number 
and  percent  emerging  during  night  and  during  day,  478;  period,  473; 
preparation  of  burrow,  noted  by  Riley,  489;  time  in  fruit,  476. 

Last  emerging  beetle,  488. 

Life  cycle,  473,  489. 

Nativity,  468. 

Number  developing  in  windfalls,  545. 

Number  of  broods,  492. 

Oviposition,  details,  498;  effect  upon  apples,  512;  period,  504;  process  described, 
500;  seasonal  conditions  affecting,  509;  time  required,  501. 


560  INDEX. 

Plum  Curculio  (Conotrachelus  nenuphar,  Herbst) — Continued. 

Pupse,  depth,  according  to  Riley,  480;  depth  in  earth,  determined  by  measure- 
ments, 481,  557;  description  of  burrows,  489;  effect  of  drouth,  491; 
effect  of  exposure,  553,  557;  mortality,  488;  period,  473,  487;  season  of 
abundance,  490;  time  to  destroy  by  cultivation,  490;  time  passed  in 
pupal  form,  489. 

Quaintance,  A.  L.,  quoted  on  number  of  eggs  deposited  by  plum  curculio,  505. 

Repression  of  Curculios : 

Arsenical  poisons,  532,  556;  apparent  ineffectiveness,  538;  commercial  spray- 
ing, notes  on,  541;  effects  on  plum  curculios,  497,  540;  equipment  for 
applying,  536;  experience  of  Brackett,  532;  experiments  by  Forbes,  532; 
experiments  by  Weed,  532;  experiments,  laboratory,  540;  experiments  in 
1903,  533;  experiments  in  1904,  541;  experiments  reported  532;  factors 
influencing,  -538;  gain  from  their  use,  548;  opinion  of  A.  J.  Cook,  532; 
suggestions  as  to  their  practicableness,  550. 
Cultivation,  545,  553,  556;  equipment,  537;  season  to  destroy  most  pupsc, 

490,  557. 

Destruction  of  windfalls,  544,  556. 
Influence  of  neglected  orchards,  556. 
Jarring,  530. 
Location  of  orchards  affecting,  556. 

Riley,  C.  V.,  established  main  facts  regarding  apple  curculio,  515;  on  number  of 
broods  of  plum  curculios,  492;  depth  of  pupation  of  plum  curculio,  480; 
time  of  appearance  of  plum  curculio,  492. 

Say,  first  named  and  described  apple  curculio,  514. 

Smith,  R.  I.,  quoted  on  number  of  eggs  laid  by  plum  curculio,  505. 

Titus,  E.  S.  G.,  quoted  on  relative  number  of  crescents  and  feeding  punctures,  511. 

Walsh,  B.  D.,  apple  curculio,  observations,  514;  quoted,  471. 

Webster,  F.  M.,  plum  curculios  developing  from  apples,  512. 

Weed,  C.  M.,  experiment  with  London  purple  on  cherries,  532. 

Windfalls,  containing  plum  curculio  eggs,  511;  destruction,  537,  545,  556; 
number  bearing  crescents,  542;  number  bearing  plum  curculio  feeding 
punctures,  542;  number  bearing  egg-punctures,  542;  number  bearing  apple 
curculio  feeding  punctures,  542;  number  and  percent  punctured-,  538,  542; 
size,  545;  source,  545. 


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